This started out of nowhere, but lately Vista has been crashing a lot. Each time it crashed I got the same error "driver irql not less or equal" which IIRC is a memory issue so I ran memtest overnight and found no problems. However upon one crash when the machine rebooted it gave me an error saying that the system boot disc had failed and to put in the system disc. I did so and even went back to the furthest restore point, it makes no difference, I cannot boot without the system disc in. Ideas? Edit: Vista Ultimate, yes it's legit.