Corsair XMS3 isn't giving many options in ASUS P5KC BIOS

First of all the motherboard that I'm using is an ASUS P5KC. I've been using a pair of Patriot 2 x 2GB PC1333 sticks for a while but one went out, so a friend of mine loaned me two of his 2GB PC1600 sticks to use until I get mine sent back from Patriot. My motherboard doesn't support PC1600 memory, but I've read that it will automatically 'underclock' it to PC1333, which is what my board uses.

With the pair of Patriots I had before, I could set my e6850's bus speed to 500 with a multiplier of 7.0 (still using a 1333MHz memory speed) and get ~3.5GHz with no problems, even with latencies lowered and other things changed)

I noticed that this RAM is set to run at 9-9-9-24 at 1.65v, but in my BIOS I don't have the options to set it to that amount manually (it goes in steps, 1.5v, 1.6v, 1.7v, etc.) so I have it set it auto. I actually have EVERYTHING IN MY BIOS set to auto, otherwise my computer restarts when Windows begins to load. Anyway, I noticed that with my old Patriot RAM, my motherboard would default the RAM at PC1066 at 1.6v (which was incorrect, it was PC1333 RAM that ran at 1.7v). Once I manually changed the volts for the Patriot RAM to 1.7v, it gave me the option for "1333MHz".

With this pair of Corsair XMS3 RAM, I'm forced to use default settings otherwise my computer completely restarts upon entering Windows. Anything I try to change, my bus speed, any of the RAM settings, anything at all, the system restarts as soon as Windows prepares to load. And I'm talking not just memory settings, ANY settings involving the CPU, FSB, or voltage.

I've reset my BIOS and tried it like that as well with no luck.

Anyone have any ideas why this might be happening? Could it be because I'm using PC1600 RAM instead of PC1333 RAM? I'm still running the PC1600 RAM at 1333MHz, so I don't see what the problem would be. Any help would be appreciated. Thanks.

The "C" version boards from what I have seen have some very quirky BIOS'. I have not seen this issue before. You may be best served contacting ASUS.