1. Ad Aware
This free anti-spyware version provides you with advanced protection against spyware that secretly attaches and takes control of your computer, resulting in aggressive advertising pop-ups, sluggish computer activity, even identity theft through stolen bank details, passwords, and credit card account numbers.
2. CC Cleaner

CCleaner is a system optimization and privacy tool. It removes unused and temporary files from your system - allowing Windows to run faster, more efficiently and giving you more hard disk space.

3. Avast! Antivirus
THE BEST free antivirus - maybe the best overall!
4. AVG Antivirus
AVG Anti-Virus Free Edition is one of the most popular solutions to provide basic security protection on home and non-commercial PCs.
5. Easy Cleaner
EasyCleaner is a small program which deletes invalid registry entries to speed your system up. Other services include: deletes all kinds of unnecessary files like temps, backups etc., search for duplicate files, view disk space usage, manage startup programs, invalid shortcuts and add/remove software list.
6. TweakUI XP
This Microsoft PowerToy gives you access to system settings that are not exposed in the Windows XP default user interface, including mouse settings, Explorer settings, taskbar settings, and more.
7. Registrar Registry Manager
A complete award-winning registry management solution with a wealth of powerful features. See site for full details ("Lite" version)
8. SyncBack
Very highly rated backup tool. Included freatures: backup (full or incremental), restore, copy open files, throttling, syncronize, compress, automate, and advanced customization
9. Abakt
Abakt is an easy to use but quite flexible backup tool that can create normal or compressed backups in ZIP format. You can create multiple backup profiles, select files and folders to be included and apply several advanced filters based on file type, attributes, size and date
10. File Hamster
Real-time backup and archiving of your files while you work. Monitors specific files on your hard drive and creates backups upon changes to those files. It also enables you to store notes about the changes that have been made. Be sure to go get the plugins from the website too!
11. AM Deadlink
Detects dead links and duplicates in browser bookmarks and text files. If a bookmark has become unavailable you can verify and delete it permanently. Additionally you can download FavIcons for all your Favorites and Bookmarks
12. Password Corral
Popular password manager. With a clean, easy to use interface, strong encryption and all the features you would expect from a quality password management program.
13. Driver Max
DriverMax allows you to easily reinstall all your Windows drivers. No more searching for rare drivers on discs or on the web or inserting one installation CD after the other. Simply export all your current drivers (or just the ones that work ok) to a folder or a compressed file. After reinstalling Windows you will have everything in one place! Very handy
14. Rock XP
Retrieve MS product registration keys - good tool prior to reinstallations, etc. See web page for full functionality