ok. So if it happens again, it will soon come. Wait and see if it does it again.
If it does, system restore.
If you want to scan ram and harddrive, i know of a good tool kit you can download.
It's called Ultimate Boot CD
It's easy to install on a CD, but if you want to use a USB it requires you to make it bootable. It's not difficult, but if you have a cd to spare, use that. That way you also don't need to enter the boot manager or BIOS to boot from USB.
But let's just wait and see for now