Here's a couple of freeware Windows XP tools that were sent in by Tim @ Majorgeeks.com.

XP Smoker 1.5.16: It fully optimizes your hard drive and CD drive's read ahead and write behind cache, optimizes 56K, Cable, & DSL to get the most out of it. It also, optimizes the display settings, filesystem settings, even your mouse port refresh rate. This program is amazing and the best thing about it... it's free! It also has 30+ Internet Explorer security settings.

Tweak FX 0.7: Tweak FX is a powerful tool for changing settings in the Windows system registry. It uses plugins, written in VBScript.