Strange One

I am trying to fix a friend's PC but I'm not getting very far with it. Basically the system boots with a POST screen and then starts windows (XP Pro) I get the XP boot screen for about 2 minutes then just when you think its going to boot into windows it comes up with the screen you usually get after a bad closedown i.e. it asks you how you wish to boot it, safe mode, normal or last known good configuration, choosing any of these options just gets you back into the POST screen and the process is repeated all over again. I tried to do a repair with the XP CD and did a FIXBOOT but it has made no difference.

Any ideas?