eh I find the more programs you load on to it to get rid of crap the slower it gets.
Thats just the nature of computers. I store all my important files on a NAS drive so its easy for me just to /reformat once a year, runs like a champ for months afterwards.
Ok one of your main problems is probbably Vista. Vista is a really sluggish OS that only sold itself on eye candy. You can manually disable its useless features like Windows Search Indexer as long as you don't touch anything critical.