I converted my Windows 7 Ultimate 64-bit system partition to GPT and now cannot boot. The error is, "No Operating System found". I can boot to the Paragon recovery disk I created, manually mount the system partition and access the data. I booted to my Windows 7 Ultimate 64-bit installation disk to try to run Repair to convert back to MBR, but the Windows installation disk says that it can't find any valid partitions and quits without letting me do anything at all. How can I use the Paragon boot disk I made to convert the GPT partition back to MBR? Or, is there another way other than the "Repair my system" option I can use the Windows installation disk to convert the GPT partition back to MBR?