My current windows 8.1 is not working i might have had reformatted some disk partitions by accident. Now when im trying to install windows 7 it says on my both disks and all the partitions either "windows cannot be installed to this disk. The selected disk is of the GPT partition style" and some partitions it says "windows cannot... the partition is a microsoft reserved (MSR) partition." Also. I dont care abou losing my data since there isnt anything important. The other drive is an samsung evo 840 250gb and the orher wd black 1tb. How do i clean these disks so that i can install windows 7 on them?