I have windows 8.1, and I've been trying to perform a system reset, but when I try to insert my flash drive with the recovery media, it says it's invalid. I talked to Microsoft and they said I have to use the OEM disk I built the computer with as the recovery media, only problem: I can't find the disk. Is there anyway that I can get a replacement disk without spending 100 dollars or could I get the ISO off some third party site and then use my product key?