Problems with Q6600

hey all... my brother bought this computer ~1.5 years ago:

CPU: q6600 lga 775, @ 2.4ghz stock
cooler: stock intel
GPU: 8600 gt 512mb ddr3 (w00t)
motherboard: intel ______, has SLi, ddr3, lga 775 (don't know what specifications tho)
hdd: 320gb seagate 7200.10 (i think)
ram: 2GB ddr3 1066mhz cl9
PSU: 700W Greatwall (who ever heard of that?! any ratings of Amps @ 12V please?)
case: Xaser VI supertower, 2 extra fans

monitor: 22" Widescreen, resolution @ 1280 x 1024
(he does a bit of gaming, but as his monitor size is well down, he has smaller GPU.)

Now the question of the day:
what is bottlenecking his system? it takes like 15-20 seconds (no exaggeration) to open a single word document... he gets alright FPS in games, but loading them still takes a while, longer than it did when he originally got it... we think its the hdd. its less than half full, and he defrags it every 1 to 2 months (with only the windows defragger)

what else is wrong with his system?
need more ram? need a newer hdd? his PSU is slowly dying?

thanks in advance,
MICK