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.