To make Windows runs faster, not more than 2 minutes you need to enter the Windows since you've turn on your computer.
To make it faster than before, you need something to do like reducing your unused icon on the desktop and using wallpaper which not needing a lot of memory. Do refresh of your computer by right-click on the desktop and click "Refresh", or press F5 to do the same thing.
Don't forget to defrag your PC, by click Start - Accessories - System Tools - Disk Defragmenter.
If you are often to installing and uninstalling programs in your PC, just clean up the registry one time in a week or more, use software to help you to do it, you can use Registry Mechanic, in trial version, you just only use 6 sections of registry to be cleaned. You can found this program by search in this blog (in the next post)
Unmark your unused program to be not started automatically, you can do it my click Start - Run, and type "MSCONFIG" inside of the box.
Anti-Virus is pretty important to protect and guard your PC from Virus/Trojan/Worm. And don't forget to install Anti-Spyware and Anti-Malware.
Additional: If name in Registered Windows XP is not match with your name, you can fix it by open Registry Editor (Start - Run : "Regedit"), click Edit - Find, and type "RegOwner". If you've find it, just left click and edit it with yourname.