So, for a while late last year, this computer was getting extremely unreliable. It was regularly spontaneously shutting itself down and restarting, often while I was in the middle of work. After a few times away being fixed (including a period of about ten days while I was actually having some time off work and would have preferred to have been getting some work done on my web site), it eventually failed completely and had to have its power supply replaced. It might not have been the power supply that was doing it, but replacing it cut the nonsense down to about once a month (which is probably normal for computers).
Except for the past few weeks it's been back to a weekly occurrence again. So I may be looking at having to get it fixed again.
Otherwise, if anyone out there knows what the farnarkle a "bug check" is and how to stop the computer doing it, could they let me know?