I've messed up my system yesterday. On my iMac I have installed OS X and Windows 10 using Boot Camp Assistant. The Windows MBR is damaged and I can't start it anymore. I get a black screen with the error message:
No operation system found
Luckily I can still start up OS X. I'm looking for a way to repair the MBR in the Windows partition. When I start Disk Utility in OS X and click "Check" on the Windows partition, it prints the following error:
Invalid BS_jmpBoot in boot block: 000000
I've already tried to repair it with fdisk, but also when I create a HFS+ MBR it gives me this error. I've tried to figure it out for multiple hours now and nothing seems to work. I do not want to wipe the whole partition because then my whole data would be lost.