We use both of these programs with Vista and XP. We highly recommend them.
You can try them at No Cost
Repair XP Pro 100% XP & Vista Compatible
(Great program) The most comprehensive system repair tools on the market.
 

If you plan on using or already have VoIP (Voice over Internet Protocol) try these test sites.
Test your Internet connection for VoIP compatibility and more: Two good testing sites.
http://myspeed.visualware.com/voip/index.html    and    http://www.testyourvoip.com

* The hottest Registry cleaning software on the Net today!

* Repair XP Pro - (Great program) The most comprehensive system repair tool on the market.

* 100's of Very Good Assorted Free computer programs.