My set up is as follows:

E8400
Barracuda es.2 32mb cache 250gb sata drive
evga 8800gt 512 mb
GIGABYTE GA-P35-DS3L LGA 775 Intel P35
arctic freezer 7 pro
raidmax smilodon case
acer 22" monitor

I was wondering what ram I should go with ddr2 1066 or ddr2 800 here are the two kits I was looking at.

G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory - Retail
http://www.newegg.com/Product/Produc...82E16820231122

or

G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory - Retail
http://www.newegg.com/Product/Produc...82E16820231166

both have the same timing and i will be ordering tonight or tomorrow based on responses of this thread.

both have 5-5-5-15 timing.

What will run faster, will the 1066 clock down or will it run faster than the 800 mhz ram. even if there is a very slight increase in speed/performance i will go with the 1066 mhz ram.

Please let me know guys as I am getting ready to order all my parts from newegg.

DDR2 800. The P35-DS3x and DS4x boards have compatibility issues with RAM natively higher than DDR2 800. However (depending on RAM), you can OC the DDR2 800 RAM to 1066+ speeds with out compatibility issues. Remember to increase the voltages once you get any of the RAM listed above. See:
http://www.tomshardware.com/forum/ [...] w=0&nojs=0
for more details, OCing help,etc.

Side note: Also just make sure you have a good PSU.

DDR2 800 is good enough... the speed difference is negligible or about 1%-5% so why pay more out of it. =)

FWIW, and I've heard some of the compatibility issues as well, but I just put 2x1GB of DDR2-1066 (Crucial Ballistix) onto a GA-P35-DS3L and it works just fine.
Are the problems more likely with four sticks?