Well, it seems that i have the same problem with the Asus 8800GT (the one with the new cooler) and i can't possibly find out what's wrong!! If everything is at default in 3d Mark 06 (default tests and settings) i get a 5818 score...I have :

AMD X2 4600+ @2,4GHz

2GB (2X1) Dual Channel Kingston 5-5-5-15 DDR2@667,

Asus Crosshair Mobo,

Thermaltake 550W PSU

X-fi Fatal1ty platinum soundcard

Everything seems fine...the pci-e bus is at 16x, nothing is overclocked or failing, the latest drivers and bios updates are installed and I recently had a clean install of my windows. I'm now running XP black edition but i'll soon switch back to my authentic XP pro since i hear alot of weird stuff about malware, though my antivirus and spyware utilities haven't found any so far...Any help greatly appreciated!!!