I know you tried defrag, but try it in safe mode. turn off ANY screen savers, too. doing this in safe mode (F8 on start before the windows splash screen, choose safe mode) sometimes helps because windows is not loading up uneeded crap. think about it like this, if anything is accessing or writing to the HDD during a defrag, then it may need to start over. although measures are SUPPOSED to have been taken to stop this, it doesn't always work. since defrag reorganizes (read and rewrite back to HDD), if something has changed, well it may need to rewrite/read certain sections. so do it in safe mode. you'll know it, because everything will be HUGE. and it'll say your in safe mode, too.