Every few years when you buy a new computer, remember to delete your personal information off the old computer - especially if the old computer will be going to a Recycler - which may end up in Poland or South Africa.
There is a software program called Complete Data Wipe that is powerful... and has the ability to delete personal directories or the whole hard drive. Be careful.
If you are giving the old computer to someone, the computer should have a Windows Label stuck on the side of the case. The label shows if it is an OEM version of Windows, a Corporate Edition, or a Manufacturer's Edition.
Remember to place the CD-Roms containing the Installer and Device Drivers inside the computer case if you choose to wipe the complete hard drive, otherwise the person will need to spend $100+ and go buy a new Windows license.
If you only want to give the computer to a friend... but without destroying the Windows Installer files that are usually on the hard drive, it is best to take the computer to one of the 1USA-Certified Computer Repair Shops for a "Wipe & Reload". Your friend will receive the computer with a fresh install of Windows - but without your personal information.
If you intend to do your own Wipe & Reload, make sure you have all of the Device Drivers (sound driver, video driver, Ethernet card driver, etc) before erasing the drive. Some manufacturers do not have Drivers on their websites... and the computer would be unuseable. (This is why it's best to take the computer to a 1USA-Certified Computer Repair Shop - because they know what they're getting into.)
Tech Support on this is available to 1USA customers from the 1USA Webmasters.