my computer is taking toooo long to shut down... about 3 mins... and the problem is exacerbating by the day...

i tried to disable all the startup apps through the msconig feature.
i have all the recent drivers.

my computer is running on
athlon xp 1.8ghz
MSI GeForce2 video card
1Ghz PC333 DDR RAM (2 at 512 each)
winxp pro
two hard drives 40G each
300 watt powersupply

windows update has been running regularly
it's a self-built system
plz help!!!