MBR apparently overwritten!

[David Cuthbert]

Petr Janda wrote:
Something freaky has happened. My 3rd disk's partitions are gone. I had a 1) 
HURD 2) Windows 3) DragonFly. Now wanting to play some games i went to boot 
WIndows and i found out the DragonFly partition is now covering the whole 
disk. Does MBR have a modification timestamp? If yes, how to retrieve it? If 
no, what can i do?
I'm not aware of a way to recover the MBR -- it's not copied to any 
backup space when overwritten (intentionally, accidentally, or via 
software bug).

You may be interested in gpart, which will attempt to guess the 
partition boundaries:
http://www.stud.uni-hannover.de/user/76201/gpart/

You probably know this already, but don't write to that disk!  The more 
you write to it now, the less likely that partition recovery will succeed.