Thanks Fugazi - no, no external attached at the time, and I understand what rdisk is but not how it can be different to the current disk allocation in Windows. To recap, XP is on Disk 1, Part 2 in Windows Disk Management, but rdisk (3), partition(2) in boot ini. I just don't trust Windows not to throw some wobbly because of this at some later stage, perhaps in defrag or a new partioning or whatever - and there was me thinking CMOS battery replacement - SIMPLE - just pop and click.................
silly me.
To answer your full question, yes, Disk 3 was not there at install - a 160GB Sata I use only for storage at the moment. That would appear to be the issue, I guess, but why?