"Windows 7 7601 not genuine" and OS won't fully boot

Thank you all. Problem's solved

I tried paragon's rescue kit but it was soooooo slow (while detecting partitions and OS) that I tried it manually (boot in safe mode > regedit through task manager etc as described in Bill2's thread). Ans it was that simple.

I had XP on C: and Seven on D:
When I formatted XP and merge C: with D:, remaining partition was still declared as D: which explains why Seven was unhappy (but why did it begin to boot then stop? if drive letter was wrong it shouldn't have boot at all?). I swapped D: to C: with regedit and everything came back to normal.

Again, thank you very much for your help

Glad you sorted it out.

Paragon must not like your hardware - usually is pretty quick.

What makes you think a drive letter change would stop it booting at all ?