|I doubt anyone will be able to be too definite about this - too many variables.|
No harm doing the Mem test, it will either find something or not. Clearly the OS got corrupted and it is still possible that the RAM (or its connectors) caused this.
As for the hard disk, if you run chkdsk /f that will give you a quick clue about the condition of the hard disk. There is a more thorough and lengthy test, if you wish to go for it, using chkdsk /r. Either way the results flash up on the screen rather fast, so if you don't have time to read how many bad blocks were discovered (if any) then a report appears in Events. If it passes with flying colors then clearly something messed up the OS. It could have just been a software glitch, where some conflict happened - by no means unheard of. Reloading the OS will have now sorted out the latter.
Always pop back and let us know the outcome - thanks