It occured when I started up the machine one morning. I've not beeen altering anything or setting up anything new whatsoever. I only use the pc for playing games basically, nothing complex or involved at all. I've never touched any hardware on it at all.

I get the error message each time I reboot, but to date I've not noticed any data loss, but the error still flags up each time I reboot the machine.

Thanks for responding by the way!

edit - I've had the pc about a year or so without any issues. It's a Dell DXP061, Vista Home Premium with a 500gig Sata HD. A smaller 10gig backup HD as well.