How do I restore a Windows 7 DMG file to Boot Camp (and make it bootable)?
Try this variation on what its stated there: 


Run bootcamp to allocate the space 2- 
Install W7
Go back to OSX (Install REFIT or similar as bootmanager (optional))
Restore your DMG image over the W7 partition


With this you dont need the fdisk commands as bootcamp should mark the partition as active (bootable).

This SHOULD work.

The problem with the linked page process is that w7 (just as osx) is actually in 2 partitions, a small boot one and a large with the OS, your DMG only contains the OS partition.