How Do You Remove a Default File Association in Windows 7?

The option to delete a file association is conspicuously absent from file associations user interface in Windows 7, so how can you delete file associations you no longer want? Read on as we explore how to remove a default file association.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

The Question

SuperUser reader Christothes writes:

I somehow have set the default file type association for a file type in Windows 7. It doesn’t appear to be possible to delete it from the “Change the file type associated with a file extension” options screen. Is it possible to remove it?

While the tool for doing so definitely moved, certainly the option to remove a file association hasn’t vanished completely.

The Answer

SuperUser contributor Peter Mortensen offers the following solution:

Find the file extension in question under this key in the registry:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\FileExts

Deleting the sub-key with the same name as the extension you want to un-associate will delete the default program association. You’ll have to kill and restart explorer.exe for this to take effect.

You may also need to remove the same sub key from HKEY_CLASSES_ROOT as well.

It takes a little longer to root through the registry in search of the file association key than to use the old file association user interface, but it gets the job done.

How to Calibrate Your Laptop’s Battery For Accurate Battery Life Estimates

So you’re using your laptop and, all of the sudden, it dies. There was no battery warning from Windows — in fact, you recently checked and Windows said you had 30% battery power left. What’s going on?

Even if you treat your laptop’s battery properly, its capacity will decrease over time. Its built-in power meter estimates how much juice available and how much time on battery you have left — but it can sometimes give you wrong estimates.

Why Calibrating the Battery Is Necessary

If you’re taking proper care of your laptop’s battery, you should be allowing it to discharge somewhat before plugging it back in and topping it off. You shouldn’t be allowing your laptop’s battery to die completely or even get extremely low each time you use it. Performing regular top-up will extend your battery’s life.

However, this sort of behavior can confuse the laptop’s battery meter. No matter how well you take care of the battery, its capacity will still decrease as a result of unavoidable factors like typical usage, age, and heat. If the battery isn’t allowed to run from 100% down to 0% occasionally, the battery’s power meter won’t know how much juice is actually in the battery.

How Often Should You Calibrate the Battery?

Manufacturers generally recommend calibrating the battery every 2-3 months. This helps keep your battery readings accurate.

In reality, you likely don’t have to do this that often if you’re not too worried about your laptop’s battery readings being completely precise. However, if you don’t calibrate your battery regularly, you may eventually find your laptop suddenly dying on you when you’re using it — without any prior warnings. When this happens, it’s definitely time to calibrate the battery.

Basic Calibration Instructions

Calibrating — or recalibrating, really, as the battery was calibrated in the past when the battery had more capacity — involves letting the battery run from 100% capacity straight down to almost dead, then charging it back to full. The battery’s power meter will then see how long the battery lasts and get a much more accurate idea of how much capacity the battery has left.

Some laptop manufacturers include utilities that will calibrate the battery for you. These tools will usually just make sure your laptop has a full battery, disable power management settings, and allow the battery to run to empty so the battery’s internal circuitry can get an idea of how long the battery lasts. Check your laptop manufacturer’s website for information on using any utilities they provide.

You should also look at your laptop’s manual or help files. Each manufacturer may recommend a slightly different calibration procedure or tool to ensure your laptop’s battery is properly calibrated. Some manufacturers may even recommend against doing this. Apple says its newer laptops don’t require this calibration procedure, although older models do.

How to Manually Calibrate a Battery

While it’s a good idea to use any included utilities or just follow instructions specific to your laptop, you can also perform battery calibration without any specialized tools. The basic process is simple:

• Charge your laptop’s battery to full — that’s 100%.
• Let the battery rest for at least two hours, leaving the computer plugged in. This will ensure that the battery is cool and not still hot from the charging process. You’re free to use your computer normally while it’s plugged in.
• Go into your computer’s power management settings and set it to automatically sleep or hibernate at 5% battery.

• Pull the power plug and leave your computer discharging until it automatically sleeps or hibernates. You can keep using your computer normally while this happens.

(Note: If you want to calibrate the battery while you aren’t using the computer, be sure your computer isn’t set to automatically sleep, hibernate, or turn its display off while idle. If your computer automatically enters power-saving mode while you’re away, it will save power and won’t discharge properly.)

• Allow your computer to sit for five hours or so after it automatically shuts down.
• Plug your computer back into the outlet and charge it back up to 100%. You can keep using your computer normally.
• Ensure any power management settings are set to their normal values. For example, you probably want your computer to automatically power off the display and then go to sleep when you’re not using it to save battery power.

Three Wireless Display Technologies That You Probably Own But Don’t Use

Want to relay your smartphone’s or laptop’s display onto a larger screen without wires? No, it’s not science fiction. You can wirelessly output video from computers and smartphones today. Wireless display technologies use WiFi to output video to compatible adapters. You only need a display adapter, which connects to a monitor and a WiDI or Miracast compatible device. Most modern devices are compatible with the technology. There’s also Apple’s proprietary technology, AirPlay.

Noticing wireless display technology on all my devices, I recently set up a Miracast adapter. This article summarizes my experience. While setup doesn’t require much effort, it can require a bit of leg work.

WiDi

Intel developed the Wireless Display (WiDi) technology as a means of streaming video and audio from compatible devices. WiDi inhabits on most modern Intel motherboards, in particular all Ultrabook-branded laptops.

Additionally, WiDi will also soon receive support for Miracast in its 3.5 incarnation, meaning that the two major wireless displays will actually converge. This is practically unheard of among competing standards. Typically, they fight to the death.

WiDi shows up in many second generation Intel Core-series processors. Ivy Bridge through Haswell can incorporate WiDi, although it does not exist on all Intel computers.

AirPlay

AirPlay, unlike WiDi or Miracast, is a proprietary technology. It’s only compatible with Apple TVand other officially vetted brands. You can’t purchase an adapter that will stream to any device, as you might with WiDi or Miracast. AirPlay’s great advantage over other wireless display standards is its ability to function with AirPlay enabled-speakers.

Apple intended for the technology to allow mobile devices to function as remote controls and streaming devices. It licenses out AirPlay to a variety of audio-equipment manufacturers — such as Sony, Pioneer and Philips.

Overall, AirPlay possesses far fewer vices and foibles than Miracast.

You can check out AirPlay in action below:

For some apps that allow you to output display to other operating systems, check out AirDisplay.

Miracast

Miracast is based on WiFi Direct, which enables handsets to communicate with one another, without connecting to a network. It uses WiFi as a direct means of interfacing with another computer. Miracast uses a variation on this technology to allow the output of audio and video, without a wired interface. However, the Miracast specification makes no provision for audio-only devices, such as MP3 players.

On the downside, Miracast is a new format. As such, it has suffered from a huge number of teething troubles, including display quality issues, lag and instability. I’ve experienced a great deal of issues related to compatibility. Miracast devices don’t work well with all versions of Android. For example, my Android 4.2.1 device failed to output display when it updated to Android 4.2.2.

How I Set Up My Miracast Device

Here’s a shot of the Netgear Push2TV PTV3000 device – it’s both Miracast and WiDi compatible, meaning I could choose to output the display from either my smartphone or my personal computer. It’s also capable of running off the power provided through a USB port. I ran it off of my display’s USB ports.

Setting it up was super simple: I plugged the device into a power source and then activated Wireless Display on my smartphone. From there, simply choose the appropriate display from the list and connect to the Push2TV device.

The Push2TV PTV3000 device wasn’t cheap – at $60 on Amazon – and it didn’t set up very easily. It required a firmware update before receiving compatibility with my Android 4.2.1. To Netgear’s credit, they continually improved the firmware until it finally functioned properly. You can watch video of it in action below:

On the downside, Miracast’s implementation in Netgear’s Push2TV device remains experimental. The most recent firmware update of my Nexus 4 broke compatibility with the Push2TV device. Also, simultaneous Bluetooth and wireless display doesn’t work; only one or the other functions at the same time. However, some custom ROMs permit both to function at the same time. Using a custom ROM, my Nexus 4 functioned briefly as a desktop alternative, pairing a Bluetooth wireless keyboard with a mouse. For the curious: You can read more about my attempts to turn my phone into a desktop-phone convergence device.