Your story is weird. Why would the "company's owners" want to crack passwords ? What could be the circumstances which would make such an effort appropriate (i.e. morally acceptable, legally passable and adequate for the pursued goals) ? The closest I can think of is if some data what encrypted with a password-derived key, and the password owner is unavailable or uncooperative -- and that's a police-vs-terrorists scenario, not a suspected-fraud scenario. My ability to detect common sense, or lack thereof, is tingling crazily. There is something fishy in your situation.
I sense an unusual amount of fear for something as trivial as this trade dispute.
The best explanation I can make is that the "company's owners" are working for a "company" which is in the habit of never involving law enforcement agencies in its dealings, and to administrate swift justice on a self-operated basis. Are you sure you want to work for the Yakuza ? Jail time could become a secondary worry, with regards to maintaining your ability to count up to ten.
That being said, password hashes stored in a Windows system are supposed to use the NT hash, which is a simple application of MD4 over the password (encoded in little-endian UTF-16). The best known preimage attack on MD4 is still theoretical only (effort in 2104, which is way beyond the reach of Mankind in general, your reach in particular), so you are back to the brutal method of trying potential passwords, possibly optimized through a precomputed table (rainbow or not).
With a good GPU, you could perhaps try about 10 billions of passwords per second. You can rent some powerful hardware at Amazon Web Services. If you consider the "Vista eightXL" Ophcrack table, it claims covering about 99% of 8-character passwords, for a 95-character alphabet (the whole printable ASCII charset) -- that's about one week of computations on the aforementioned GPU. Rebuilding the rainbow table itself would be done in a fortnight. Is that worth 1000$ ?
There again, fishiness oozes under the door and permeates the atmosphere.