ASUS P4B533-E Problem

Hi guys how are thinks going well I think i have a problem with my motherboard not sure have any of you guy have this problem my motherboard which is a asus p4b533-e shuts down completely every 2-3 days with out any errors when it does happen only when I go to sleep overnight in the morning the computer is shut down completely not sure what it is do you guys think it may be my motherboard or maybe something else thanks for the help guys

PIV 2.26B @ 2.821mhz 165fsb 219x2=438 memory
memmory settings 2-3-3-6
corsair xms pc3200 cl2 512mb
volcano7+ cooler
P4B533-E 1009E Raid bios
ATI 8500 128mb
sound blaster audigy platinum
winfast xp2000 tv tuner
plextor 40/12/40a
pioneer dvd 106slot
WD 1200JB 120gig
Antec true power 550watt P/S
Windows XP & SP1
Windows Plus
I think thats it

Hi guys again well I just exchanged my power supply lets see what happens hope problem goes away thanks guys