Mainboard :   Asus P5E
Chipset :   INTEL X38
Processor :   Intel Core 2 Duo E6750 2666 MHz
Physical Memory :   4096 MB (2 x 2048 DDR2-SDRAM )Corsair ddr2 800 mhz xms2-6400
Video Card :   NVIDIA GeForce 8600 GTS
Hard Disk :   ST3750330AS (750 GB)
OS: Windows Vista Ultimate

I want to install another four gb of RAM but the computer wont accept it and it shuts down. Its the same RAM exactly as installed now. Any suggestions
32-bit, or 64-bit Vista?Check your Motherboard specs, and see if the board can support it, some boards limit out at 4 GB or less even, most new boards can handle eight, but not always.It is 64 bit. I have read the manual that came with the motherboard and it says it will accept 8 gb
It wont even accept 6. I put the sticks in one at a time to try it and no luck.Have you tried to start the comp with just the new ram to see if it will work? What RAM ? ?
Same speed and specs that's in there now ? ?
Some ASUS boards need settings changed in the BIOS in order to max out the RAM.Yes the new RAM works when I take out the old. I set the bios to default, but am not sure how to change it if I had to, or what changes to MAKE. Yes the new RAM is exact same specs as the ones installed.4 x DIMM, max. 8GB, DDR2 1200 / 1066 / 800 / 667 MHz, non-ECC, un-buffered memory
Dual channel memory architecture
* DDR2 1200 is O.C. speed
* Refer to www.asus.com or this user manual for the Memory QVL(Qualified Vendors Lists).

So yeah U can take up to 8GB of ram, but are the sticks ALL the same speed?

Is your PSU grunty enough to handle the extra pull on the 1.5V?

Kurtiskain, when I bought the extra RAM it was the exact same specs as the RAM that was installed. When I removed the old RAM and installed the new, it worked. So this afternoon I tried one stick from the old and one from the new and it didn't work. So even though the specs on the RAM are identical, they aren't COMPATIBLE with each other. I phoned the company and they said to return all four, which I did and ordered a new set of four.
Corsair XMS2 DHX 8192MB PC6400 Memory - DDR2 800MHz Dual Channel (4x2048MB

Hopefully that should solve the problem. Thanks for your help everyone.