The above thread has the same problem as me. My sister has an Acer Aspire L5100 and I ordered two sticks of 2GB for the computer.
Both sticks work fine, but if I put both sticks in then the PC doesn't seem to post. I put one of the old 512 sticks plus a 2GB stick in making total of 2.5gb and it posted. So the 2gb maximum for mainboard seems not to be true.
I had trouble getting into bios as well, but after resetting cmos, I could get in via pressing del.
Now there is a bios upgrade for this computer which I downloaded off the acer website, it's build R02_A1 I think, it comes with a winflash utility and a .bin file. I think flashing the bios will solve the problem.
The only problem is I cannot flash the bios. I load up the winflash utility and click on update bios, select the correct bios (.bin file) and after a few seconds it says "please select correct bios".
Can anyone give me an idea how else I can flash the bios .bin file. I have tried all avenues.