> I had to reformat my harddisk. After copying back my 
> HTTrack  websites and reinstalling WinHTTrack 3.31 I can 
> no more access the saved sites through File>Browse sites. 

Did you setup the path in WinHTTrack (first screen, "Base 
path") correctly ? Then it should work (and the index will 
be rebuilt automatically next time you mirror a site)