ugh, soo I finally got a new gaming rig to play some new games, and that part of the new pc is awesome, runs games great....however I am having a Real problem with Logging off a user in windows or Turning off, shutting down/restarting the PC

Now, switching a user in Win XP, no problem, takes like 5 seconds max switching users, but loggin off the user, or turning off pc, sometimes it does it in about a minute, other times it takes 5-10mins waiting to shut off/log off....WTF

!
then, a couple of times it does not shut down at all, waited like 20mins (after clicking on 'turn off computer') one time and I had to cold shut it off holding the dam power button until pc turned off

PC specs are
HP amd dual processor w/2 gigs of ram
320 gig HD, about 200 free
im running the norton anti-virus that came with the pc, have adaware spyware installed aswell.
this happened right out of the box, 1st nite I had it, was on maybe 2 hrs, didnt think anything of it, now that it's happened 3-4 times now, I need some help, Ive put a bunch of stuff on it already and dont really want to exchange it, but its frustrating me that If it does it again, I'll bloody do that
any help would be appreciated...
thanks,
Gav