DQ965GF supports a maximum of 8GB disposed on 4 slots. I bought 4 x 2GB DDR2 800Mhz and the bios setup recognizes 4 bank of 2GB in dual channel manner, giving a 8GB total ram. The linux memtest recognizes 8GB also.
I searched for its specifications on Intel and I discovered this MB support only 4GB for 800MHz and 8GB for 667 or 533 MHz.
It's amazing and seems to play a loosing game.
Refer to http://downloadmirror.intel.com/15033/eng/DQ965GF_TechProdSpec.pdf.
I got success installing Ubuntu 10.10 amd64 but the 'free' command shows only 3,260MB of total ram.