If you have a regular Windows disk and you only have access to WiFi Internet, you will want to download the drivers to a disk so you can reinstall them after finishing your new Windows installation. Some computers come with vendor restore CDs. These should include the drivers for the hardware your computer came with from the factory.
If you're using a copy of the OS that came with your computer, you will need to know the product key. This will be on a sticker placed on the back of your desktop computer or the bottom of your laptop. If you have a retail copy of Windows, this product key sticker will be on the CD case. You can see pictures of these stickers here:
Back up your data. You can probably restore your OS without overwriting any other data, but there's always a chance you will accidentally reformat your hard drive.
Insert the Windows CD and reset your computer. You will see a message saying either "Press (key) for BIOS" or "Press (key) for boot options." Press this key, and use the menus to tell the computer to boot from your CD drive.
The computer will now load a menu from the CD. You will have several options, but since you're reinstalling you will want to pick the "Restore" or "Easy Transfer" installation. You will now be asked which type of keyboard, currency, and language you use.
Next you will be asked which partition you want Windows installed to. If you have a dual-boot system, you will see at least three partitions. The first partition holds boot information, and the third holds your other operating system. Windows should be installed to the second partition.
Once Windows has been reinstalled, your computer will restart. Remove the CD from the drive. The first time you boot you will be asked to verify the operating system with Microsoft. You will need to use an Internet connection to do this.
Posted 3423 day ago