DP45SG: Unable to get RAM working. 3 beeps.

My mobo is DP45SG with Q9550 C2Q proccy. The system runs on Corsair 650TX.
I have been using transcend 2x1GB 1333Mhz ram until now.

Recently a friend of mine got me Corsair XMS3 2x2GB ram as a gift. I did a little researching I found out that the corsair ram was rated at 1.65v and my old ram and mobo are rated at 1.5v. So, I tried changing the memory voltage to 1.65v while using the transcend ram in the bios, then powered off and used the corsair ones. Pc refused to boot gave me the three long beeps. I tried all possible combinations of the ram, and finally when my PC refused to boot, I had to reset the CMOS. Kept the XMS3 aside.

Two days back, I got myself a Transcend 2x2GB DDR3 1333 CL9 and put it in my mobo. Even then it gives me the three beeps and won't boot. But when I put back in my old Transcend 2x1GB DDR3 1333, pc boots fine. I confirmed the voltages and the new ones are indeed rated at 1.5v but still won't work.

I tried swapping between my old 2x1GB ram sticks and they work fine. But the new ones I bought, transcend 2x2GB sticks do not work in any combo I tried, even individually and along with the old ram. As of now I am stuck with 2x1GB DDR3, even though I have 2x2GB transcend and 2x2GB corsair with me.

I tried updating my bios hoping it might solve my problem, but once the PC shuts down, it simply just stuck during the boot and nothing comes on the display. I've let it stay that way for more than an hour and then I had to manually restart to find that I still have the old bios version.

I've also tried manually setting the ram voltage to 1.6v and 1.65v with old ram and trying on the new Transcend ram. Also I've tried to run the old ram at 1066 and then added the new ram. Both of these times the pc refused to boot and gave me three beeps.

I use my pc for photoshop, illustrator and video editing. So I really need more ram to run these smoothy. I was hoping to switch to 64-bit once I have the 6Gb ram I was hoping for. But sadly I can't find any way to use the new ram sticks I have.
I seriously think my mobo is causing all this trouble but I'm not sure. What can I do now? Any way I can workaround this problem and use the new ram sticks I have? What could be the problem? Or is the only way I can proceed is to get a new mobo and cpu?

With only the 2 x 1GB Transcend modules installed, manually change the timings to 9-9-9-27 (tCL, tRCD, tRP, and tRAS; all sub-timings on Auto) w/ the DRAM voltage set to 1.70V at DDR3-1333. Then remove the modules and install the 2 x 2GB sticks of Transcend in DIMM slot 0 of Channel A and DIMM slot 0 of Channel B (1st and 3rd slots).

I did as you said. Rebooted into bios and changed the timings to 9-9-9-27 and voltage to 1.7v. Then switched off the pc and swapped the 2x1GB for the new 2x2GB ones in the 1st and 3rd slots. Powered it on. Still, it gave me the three beeps with no display. It refuses to boot.

Try loosening the timings to 10-10-10-27. What voltage options besides DRAM voltage are available if any?

I'll try loosening the timings to 10-10-10-27. Memory voltage options available in the bios are from the default 1.55v upto around 1.9v with increments of 0.05v I think.

2GB per slot id the max my mobo can support. Just checked to avoid doubts.

I think you misunderstood me. What voltage options besides DRAM voltage are available? Assuming you have a MCH/ICH voltage option, leave the timings at 9-9-9-27 but bump MCH voltage to 1.3V, and change tRFC to 80-88.

Got the mch voltage option in processor override and made it 1.3v with the memory timings you said. Still no luck, got 3 beeps and refused to boot.

You need to get the BIOS flashed to the newest revision.

I even updated my bios to the latest version available on intel's website. Still no luck. Getting the three beeps on boot.
Is my mobo acting weird? Anything wrong with it? I've heard the dp45sg board has bugs and isn't very stable but nothing like this.