For a start you can remove any of the excess rubbish that Windows in general likes to have sitting around by navigating to: Start > Control Panel > Programs and Features > Turn Windows features on or off.
Remove the things that you won't need for your PC, like tablet PC and windows meeting space etc.

I usually turn off all the eye candy on gaming PC's since i personally can't stand all that crap. Right click Computer > Advanced under performance click settings. Choose "adjust for best performance" then apply. Then go "custom" and turn on these 3: smooth edges of screen fonts, use drop shadows for icon labels and use visual styles on windows and buttons. Whilst you're in the performance options click the Advanced tab and under Virtual Memory click change. Click "no paging file" > set then reboot. Once it has rebooted go back into this option and set it manually. This puts the paging file at the start of the disk which makes accessing it faster. Make the initial and maximum sizes the same. If you have more than 4Gb PHYSICAL memory set it to 512Mb. DO NOT SET IT TO 0, WINDOWS NEEDS A VALUE HERE!!

I'd also recommend getting a good commercial defrag program and defragging a few times once you have your initial setup done. Ones like http://www.diskeeper.com/ , http://www.oo-software.com/ or http://www.raxco.com/

Do a thorough disk cleanup. Click start type "cmd" (no quotes) in the search box, hit enter. At the command prompt type (without quotes): "cleanmgr /sageset:1" hit enter. In the disk cleanup settings click all of them then ok. Then at the command promp type (without quotes): "cleanmgr". Choose the drive, click ok. Choose what you want to remove then ok.

Get a good registry cleaner, the one mentioned in that Vista tweak forum seems alright. Also optimize the registry with NTREGOPT found here: http://www.larshederer.homepage.t-online.de/erunt/

You can also use crapcleaner to give it an even more thorough cleaning: http://www.ccleaner.com/

JV Power Tools is also pretty rad for doing some optimization: http://www.macecraft.com/

phew....that should make it fly!! 8)