welcome to the forum.. Vista already comes with a couple of cleaning and maintenance utilitys.. These can be found in the start menu with 'Disk Clean' dealing with old web pages and folders as well as a Defragmentation utility for your hard drive. Using both on a regular basis will go a long way to keeping your os running nice and smooth.
I also use a utility called Ccleaner which is free and can be downloaded here: Download CCleaner 2.08.588 - FileHippo.com
This is like an advanced version of the disk clean utility and will also clean the registry too..
If you would like more reading on the subject and also have an excellent guide then try the 'Tweakguides' for vista which again is free and available from here: TweakGuides.com - The TweakGuides Tweaking Companion
You'll need a PDF reader such as Adobe Reader or Foxit (you can google for the download)
If you need any more advise please post back...
Use regCleaner 4.3 dated back in 2002!
I found it a month ago, and even though ccleaner is also good, I got surprised of the ease of use of the program, the very small size and the amount of things u can safely delete...
You can find it here |MG| RegCleaner 22.214.171.1240
Right now is a part of the jv16 power tools 2008.