PM'd you as well.. would be glad to help..
or if you want to have a go, i'd suggest running a search of the whole machine for wallet.dat and hope that one turns up with a pre-re-install modified date, copy that for backup, and attempt to recover by loading it into the new install and re-scanning
All this can be done without exposing the private keys.
If you're pretty sure the .old copy was overwritten somehow, copy it elsewhere for backup anyways, right-click the original for Properties, and see if you have "Previous Versions" you can restore. This feature may or may not have been set up automatically..