For reasons as yet unknown to me this afternoon I've started getting blue screens indicating Windows has encountered a problem and needs to restart. They have been caused by Critical Structure Corruption (NTFS) and one that just happened was caused by Win32Kfull.sys. The screen doesn't stay open very long so the wording of the error may not be exact. It seems to be happening randomly and one time rebooted when I wasn't even using the machine. No idea what is causing it to happen.