Sorry to necro the thread but it's a popular search result in google for the query so thought i'd help out anyone with the same problem.
I was having this same problem with a 16GB drive, running XP, and the only solution was to download the new version of RMPrepUSB from http://www.rmprepusb.com/. It went off without a hitch after that.
grubinst.exe could not make a backup of MBR of disk #3
in Install Windows from USB
Posted
Sorry to necro the thread but it's a popular search result in google for the query so thought i'd help out anyone with the same problem.
I was having this same problem with a 16GB drive, running XP, and the only solution was to download the new version of RMPrepUSB from http://www.rmprepusb.com/. It went off without a hitch after that.
Regards.