I have a thinkpad running win7-64 off an mSATA boot drive. I had hoped to convert the MBR to GPT using partition manager 14. After the conversion, the disk was unbootable. I tried the BIOS set to Legacy first or UEFI first, with no success. I ended up recovering by booting with Paragon recovery media, then converting back to MBR. The disk was still not bootable, but I then used a win7 install disk to do a repair. Any suggestions about how to do this?