If your computer has a recovery partition, run your manufacturer's recovery tool to reinstall Windows. On many PCs, you'll have to press a key during the boot process to access the recovery tool. This key may be displayed on your screen. It should also be printed in your computer's manual.
If your computer comes with a recovery disc, you can also insert it in your computer's optical drive and boot from it to begin reinstalling Windows. You'll end up with the manufacturer's like-new Windows system on your drive. All the original drivers will be installed, which is good, but all that nasty bloatware will also come back--that's bad. You'll have to remove unwanted junk software after you reinstall.
Download Windows Installation Media
Refresh, reset, and manufacturer-approved recovery tools may not help you get a clean, fresh Windows system. Reinstalling Windows from a Windows installation disc will.
If you've built your own PC and installed Windows on it, you should have a Windows disc lying around. If you don't have a disc, you can download Windows 8 or 8.1 installation media from Microsoft or download a Windows 7 ISO file from Digital River. You can find the product key currently in-use on your Windows PC with a tool like NirSoft's ProduKey. Write it down--you may need it later.
The Windows 8 and 8.1 tool will guide you through creating USB installation media. If you've downloaded a Windows 7 ISO file and you'd rather not burn it to disc, you can use Microsoft's Windows 7 USB/DVD download tool to put that Windows system on a USB drive and install it from USB.
Boot the Windows Installation Media
To perform a clean install of Windows, insert your installation media into your computer's optical drive or USB port and reboot. Your computer should automatically boot from the removable media.
If it doesn't, you may need to enter the computer's BIOS and change its boot order or press a key during the boot process to access a boot menu and choose a boot device.
New Windows 8 and 8.1 PCs with UEFI firmware allow you to choose a boot device in a different way. From within Windows, hold Shift and click the Restart option on the Settings charm panel or on the Start screen. You can also open the PC settings app, navigating to Update and recovery > Recovery and clicking Restart now under Advanced startup.'
Your computer will reboot into the Advanced Startup Options menu. Select Use a device and choose the device you want to boot from. If your computer can't boot Windows properly, don't worry: It will boot directly to this menu so you can use these options to help fix things.
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