problems w/ vista 32

HI,

My windows explorer is very slow these days. It takes like a minute to open my computer for example, but once it is opened, everything seems fine. My computer runs on vista 32, but i doubt that is the problem. I wonder if some of the changes i've done to my desktop may be the cause of the problem. This is a list of what i've done recently:

1. changed by psu and gpu (corsair vx 450 and bfg 8800gt 512mb)
2. Moved quite a bit of files to my portable harddrive (about 50GB+)
3. Installed some games: crysis and COD4

I've done disk defragmenting quite regularly so the system boots up quite fast. But windows explorer still lagged alot. But other softwares works just fine, its just the windows explorer i'm having problems with. i've also done system recovery set to a week ago and it still didn't fix it.

If anyone had this kind of problem and knows how to deal with it or if you just know the solution or have any suggestions, please tell.

Thanks