Windows XP and DDR2 1066 not getting along

Hi everyone, I wanted to see if maybe anyone could help me with an issue that I'm having.

My motherboard recognizes my Ram as DDR2 1066 but when it goes to load into Windows XP it never makes it to the blue loading screen and instead restarts.

Everything works fine if I go into the BIOS and change the Ram to 800 instead of 1066.

I'm wondering if this is still a motherboard issue or if its a Windows XP issue since everything works fine until I try to load Windows.

Gigabyte MA790FX-DS5 (F6 Bios)
Athlon Phenom 9600
Patriot DDR2 1066

If anyone has any ideas I've love to hear them. It just drives me nuts thinking I may not be getting the performance I could be!

Sorry it took me a while to get back to reply but I've been a bit busy lately.

I believe the RAM was auto setting to 1.90.

I've tried adjusting the voltage of the RAM to 2.1 and under and just over that and I'm still getting the same problem.

I'm not getting a blue screen at all.

You get the black Windows XP screen with the little loading bar but it never gets to the blue Welcome screen; it simply restarts.

Windows XP seems to hate trying to run my Ram at 1066 and insists that I put it to 800.

I was using SP3. I tried uninstalling it.

Still no go. This time I didn't even get the windows loading screen before the computer restarted itself.