Oh sorry. There is a hacked version about, and that's exactly what it does crash, either just the game or the whole computer, after about five minutes.
So, not being that, it must be something like your screen saver cutting in.
Mind you, Blood is tempermental. Not really to do with Glidos: Blood doesn't like running in the XP environment. It seems to work for most people though - and if it does fail, its usually right from the start, rather than after five minutes. For me, it always fails the first time I try to start it, but works the second.