Windows 7 64bit will not start on 4 to 8GB memory increase

I installed Win7 x64 on a Dell 390 OK with (2) 2GB DDR2 667 memory. When I add 2 more 2GB DDR2 667 sticks, it will not boot in normal or repair mode. The Dell 390 system memory check states 4 identical 2GB sdram.
Tried several times and had no luck. Removed 2 sdram, back to 4GB and it boots fine.
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majidhajaliConnect With a Mentor Commented:
it may because of a failed RAM Module. try to add ram modules one by one and see the result.
You get any error or just wont boot Windows?
Do you see POST? Can you see if BIOS can detect 8GB Ram?
Some motherboards hate 4 DIMMs and you have to increase voltages a little to make them work.
Iain MacMillanIT ManagerCommented:
use Ultimate Boot CD ( and run some diagnostics on your motherboard and RAM.  As already stated, try booting with one module at a time.  Could be faulty module or dimm socket.

also does it boot with 3 modules (6GB)??  As Cantoris said, some PC boards need some tweaking to allow all memory sockets to be used, had this issue with a desktop system when running with 8GB it crashed and bluescreened, dropped to 6GB and the system was stable and working fine.  Not all bios's allow you to tweak voltages, such as mainstream manufacturers.

also helps if the modules are ALL identical.
mgreenleafsrAuthor Commented:
Thank you all for your suggestions. After playing checkers with the RAM, I found the bad one and am running with 6GB at this time.
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