corrupt disklabel, how to restore?

[didi]

I did what you shouldn't do. I have two disks one 80gb and one 100gb
I was not happy with FreeBSD 5.2.1 so I downgraded to 4.10.
Problem is the disklabel on my second drive somehow got corrupt, on this 
drive i backed up all home/* folders etc and so on, but now I can't get 
to my backup.
I really need a way to restore the disklabel.

I have tried scan_ffs with no result is there any other way,

The disk was mounted as ad1s1d one large slice.

Any information could be usefull