[all variants] How can I create partition table around partition image?

I have dd dump of NTFS partition. It mounts OK (loopback), I can access it inside XEN as well.
But because it's only a partition (sda1) without partition table and MBR, I cannot make it boot (fixmbr destroys it).

So- what would be the easiest was to build partition table around this dd image so fixmbr from recovery console would make it boot? (one partition, mbr and that's it)?