Problems installing DC RAM

[Ceer]

Hello!
I've got a problem installing my DDR2 PC2-4200 dual channel ram onto my motherboard.
ftp://ftp.dell.com/Manuals/all-prod...x_desktop/optiplex-740_user's guide_en-us.pdf
^It's the mini tower; all the info you need.

the motherboard supports 533-, 667-, or 800-MHz DDR2 SDRAM, 256 MB, 512 MB, 1 GB, or 2 GB non-ECC
and min is :dual-channel: 512 MB, single-channel: 256 MB

When I install the ram onto the motherboard, I get a 1-3-2 short beep sequence. On the manual it says it's "no memory" but i have another 1 gb stick that is fully functional. The lights 1 and 3 light up. The weird thing is; when I install the ram while on the bios menu, it shows up fully functional. But when I exit the bios menu, it automatically resets the computer and I get the error when booting up again.
I've tried all combinations, and have replaced my CMOS battery.
And ideas?

 

[fireberd]

I used to do a lot of support on the Dell community forum. Dell's have a history of compatibility with non-Dell branded memory. For that reason we always recommended Crucial Memory as it is guaranteed to work in a Dell.

There is no pattern on whether non-Dell branded memory will work or not work. It can work in one and not the other. Except, Kingston Value RAM (KVR) almost always had problems.

Crucial USA - scan results

 

[Ceer]

But, the thing is, the BIOS recognizes the ram if I insert the stick AFTER booting the computer. Is it normal to recognize it but not be able to fully boot afterwards?

 

[fireberd]

Memory (or other cards) should NEVER be plugged in or unplugged with power on the PC. You chance blowing the memory or even blowing the motherboard.

I have no idea why it recognizes it or that it even works plugging it in like you are doing. But plugging in when you do, is bypassing the self test.

At power on, the first thing the PC does is a "POST" - Power On Self Test.