My PCI-E cards are not detected by my computer!!! I think I need to disable onbo

[mystic1knight]

I have made it work before by setting "memory buffer size" to "disabled" in BIOS. (I think)

But it won't work anymore and I have to use my onboard video.
Does anybody have any ideas of how to fix this?
Maybe flashing the BIOS?
PLEASE HELP ME ANYBODY!!!

 

[knotknut]

Post your system specs.

 

[mystic1knight]

Emachines W3107
Motherboard K8MC51G
1.5gb ram
1.8ghz processor
nvidia 6100 onboard video
trying to get a pny 8600gt on (but my old 7300gs doesn't detect either, although it used to)
300 watt power supply