I know there are lots of programs out there that cah recover lost data but the most important thing to do is to NOT use that computer at all anymore! The more you use it, the less likely the files are going to be recoverable.
Maybe this software will help...I know there are tons of other ones out there though. Recover It All
I had a good result with Active Undelete, $40. Recovered some 26 GB of deleted files down to the last byte. The program recommends that the files be restored to another drive, other than the one containing the deleted ones (even firewire is OK).
What about this. If you captured them with Vegas, are they still listed in the bins or the media management window? You may be able to just select them all and tell the computer to "recapture" them all. Might take some time, but it might take less time than going to the store, buying software, installing software etc... I've done the recapture clip before. The system already knows where on the tape it lives.