Your recovery/restore disk will format your drive for you and reinstall everything back to what it was the day you bought your PC. It's [Or should be], an easy operation to do, just insert the CD Might need to re-boot, then follow the instructions on screen. They should be easy to understand and will require only a click of your mouse here and there, and for you to enter your personal details.
Remember though, you will lose all your personal files, settings and any hardware drivers you have installed over the years. Make sure you have these drivers to hand before you start. Also you will need to note your ISP and settings, unless you also have CD for this as well.
Once done, do a defrag of the drive and it should run like new. Others will advise on things I have missed, good luck, think you will be surprised at how quick your PC will be afterwards. j.