Intel doesn't show that your board will support a 4 Gb DDR2 module, so if you want 8 Gbs you need to go 4 x2 Gb. you really don't need more than 4 GB's for most things so I would just get 2x2gb DDR2 800 sitcks and save yourself some money.
THG's Memory article:http://www.tomshardware.com/reviews/ram-memory-upgrade,2778.html
this chart shows some of the tested sticks:
DDR2 compatibility chart. I would suspect that current Kingston or Crucial 2 Gb sticks would work fine. or just google the model number on the chart for 2 gb sticks if you want the exact modules listed.http://www.intel.com/support/motherboards/desktop/dg33fb/sb/CS-026593.htm
on the OS/MB compatibility chart. 64bit win 7 is supported "as is" which I think means that the only drivers are probably for vista and should work, but they didn't make specific ones for win7...http://www.intel.com/support/motherboards/desktop/sb/cs-008326.htm