I'm upgrading a PC for a friend, and have run into a problem with upgrading the motherboard. I've been assembling custom PCs for the best part of a decade now, so I'm happy enough with the basics at the very least.

The motherboard, CPU and graphics card were all updated at once - after this was done, the machine POSTs but the PCI wireless card, as well as the PCI-E graphics card, do not seem to be recognised at all by the system. No trace of them anywhere in the BIOS, or the POST output, or in Windows. I booted into Linux and ran an lspci which also showed up no sign of them.

What is the best step to go about diagnosing this? Is it likely/feasible that the motherboard's PCI bus is just defective and it needs to be RMAed? Are there any other common gotchas that might cause these symptoms?

For reference, the components in question are:

• CPU: Celeron E1400
• Motherboard: Gigabyte GA-G31M-ES2L
• Graphics card: TBC (a low end card from a couple of years ago; worked flawlessly before the mobo change)
• PCI WNIC: Edimax 7128G

Thanks in advance for any help.