For those still paying attention.
I am now running Win7 off my old 20GB IDE hard drive.
The machine refused to detect the new 1TB SATA hdd I got from IC at all - it does not even show up in computer management now. It seems to get warm when plugged in, so I imagine that it works. Other than that, I did not have a blank SATA drive one which to install Windows, hence resorting to the IDE drive.
It seems to pick up my other SATA HDD's; however this does lead to the occasional BSOD, so I have taken them all out.
I still get that same error relating to CMOS settings occasionally, and then the BIOS appears to reset itself and I have to reset the time and date again. But then it works. And it works fine once it has booted and everything.
I have not changed anything else. The only things which are not new are the CPU, the RAM and the case.
I reckon I will just soldier on until I can afford to replace the whole thing and get a completely new machine with all new parts (even the case). I am not sure what else to try...