The only recent change I can think of is that there was a Microsoft auto-update installed a few days ago. I'm not sure whether it's since then that I'm unable to boot in normal mode.
I ran AVG anti-virus in Safe Mode and it came up with some errors saying "Partition table (MBR) reading error" and "Boot sector of disk reading error" but am suspicious of their truth as surely you're past the MBR and boot when it's reached the Windows XP load screen?
Anyway, any help and advice appreciated.
Thanks.