First of all, I'm not too familiar with PC building nowadays. I used to be but haven't built my own for 10+ years, and things seem to have changed a bit since then - stupidly decided to build from scratch anyway
The problem seems to be the GTX 560. I can install the drivers (http://www.nvidia.co.uk/object/win7-winvista-64bit-285.62-whql-driver-uk.html) fine, and the card is recognised without any issues. Games play fine, and after restarting everything still works the same. When I cold boot, Windows hiccups and goes into repair mode. After declaring it can't find any issues and restarting, sometimes this repeats but eventually it boots in fallback VGA mode with the GTX drivers showing error code 52:
"Windows cannot verify the digital signature for the drivers required for this device. A recent hardware or software change might have installed a file that is signed incorrectly or damaged, or that might be malicious software from an unknown source. (Code 52)."
I know the error code suggests it's just a driver problem, but could this be caused by a hardware fault? e.g., a mistake on my part when powering the card? It is powered by 2 x (2xMolex -> 6-pin) adapters (something about this seems dodgy to me, but I dunno...)
If not, is this a known Windows or NVIDIA thing? I've had a look around and I can't find any obvious solutions.
Ok, I've fixed the problem - it turns out I was drawing way too much power from a single rail. The PSU I got wasn't fit for purpose, so I got one with better PCI-E support (i.e. 3 dedicated PCI-E 6-pin rails)