|Oh well, that seems to still keep the posssibilities open I'm afraid (hardware or software). If it turns out to be hardware then it's a pity to mess with the software but we might have to take that chance.|
Not sure if you know how to get into BIOS but if you can make it to that it would give more confidence in the hardware, therefore less in the software. It is usually either the F2 key or the Del key. I'm not suggesting you alter anything there - just exit without saving settings.
If you can get to BIOS and it's behaving well enough to make it to safe mode then there is always system restore. This should keep all your own data but you would need to use a restore point dated as near as you can guess to "just before" the problem came along.
There is one other way to prove whether it is hardware or software and this is to try booting it from a Linux Live CD. If it runs that then it is a Windows/Software issue. I can advise further on that option if need be.
Wish I could be more definite.
Always pop back and let us know the outcome - thanks