I've got two computers from Dell, they refuse to support 64bit vista as they simply don't have the time. (insider knowledge)
To get maximum memory access I've installed Vista 64bit ultimate on both machines, no problems at all.
On one system: I can't stick more than 2 memory sticks into the 4 available in the machine without it refusing to boot up.
It is currently running on 2 x 4GB sticks quite happily.
The other system is built around a Foxconn G33M02, I was wondering before spending a lot of money on 4GB sticks, which I'm having trouble finding anyway, if the machine should be capable of running 4 x 2GB sticks?
Would this just be a bios or motherboard setting problem? The error with the previous machine running at 8GB was fully updated with the bios and made no difference. It still wont allow me to put in an extra memory stick, or to run 4 x 2GB sticks in it.
Without knowing what Dell system and board that you have it would be impossible to determine what the memory limitation is in the bios.
On the other machine that is based on the Foxconn G33M02. it is capable of running 8GB total memory with the foxconn bios, however, if this is a dell, you may want to go to the Dell site and verify that this model can be upgraded to 8GB total memory as the bios is custom tailored for Dell.
As a general rule there are not many DDR2 boards that support greater than 8GB memory.