No video, POST sticking

[Pan Wah]

Hi, I'm trying to fix a PC for a friend, but getting nowhere, slowly and painfully.
It sounds as if it starts (all fans, including on GPU, & HDD spin up), but nothing ever appears on the monitor.
I have tested (and passed) the monitor, the lead, the GPU (tried another card in), the PSU (tried another PSU in), reseated EVERYTHING, reset CMOS, tried without non-essential hardware.
I also put a POST test card in, it gave a code corresponding to "waiting for video device", but the graphics card is definitely ok (as I say, I tried another, new one in).
Any ideas please?
Thanks for your help

 

[dasbufort]

Try swapping the memory, make sure you only have one stick in whatever the mobo manufactor designates as the first slot, reset the cmos and try again. This has happened to me multiple times, and every time it has been the memory.

 

[Pan Wah]

Thanks, I'll try that.

 

[Pan Wah]

Well done, got it in one - I replaced the bad stick, good as new!
Thanks again.(y)