Bought the windows 8 upgrade online from MS in Oct 2012 and upgraded from OEM windows 7 system. Upgraded again in Oct 2013 to windows 8.1 Started experiencing some OS problems and attempted system restore to earlier time and got the following error message 0x8007051a "an unspecified error occurred during system restore" and the consequence was I couldn't restore to an earlier time. I attempted to do a refresh my pc but was asked to insert media as there were files missing. Tried inserting a disk I had made when I had windows 8 and it would not work. I have the product key from the online windows 8 download I purchased and the product key for the free 8.1 upgrade I did this Oct but I have been reluctant to go to the next step of reinstalling windows option in case either of these product keys don't work. Any suggestions???