I'm looking at a machine for a friend, which has a 80GB Maxtor SATA drive and has just recently started refusing to boot up, giving a "Invalid System Disk" error.

OS is XP, BIOS sees the drive OK as does XP setup when booted from the CD.

I had thought that the MBR had become corrupted, but running fixmbr under recovery console hasn't fixed it. A full format and re-install is not a problem for him, but is there a quicker method to fix it, and also I'm interested to know what might have caused this in the first place?

could be the SATA controller I suppose, I had a funny thing with the bios when i overclocked my ram too much, the SATA raid controller stopped working and it would give funny messages.

IMO, you should try updating the SATA controller bios (and the normal bios if its integrated) and then try clearing the cmos. That might save a format, but HDD don't screw up by accident, its normally hardware failure or user 'error' (hard reset or something that has corrupted it).

Could just be on its last legs though, it making any funny noises?

Thanks for the pointers Spud.

I'll try upgrading the mobo bios and the SATA driver. It's an ASUS mobo and XP doesn't even see the drive without the asus RAID driver installed. I don't think the drive will be on its last legs, as it's only 6 months old but given my 6 month old motherboard went pop - who knows?

Operator is a 13 year old kid, so operator error looks extremely likely.