as mr s1 said, finance companies score you down for having a vt on file just like having missed payments etc. its better to ask the company for the rights to the car, sell it, hen pay off the balance in cash as that way you keep your credit rating intact.
i have recently just sold my car that was on finance althought i used the money to buy another car, the finace company declered no intrest in the car as i had been a good boy! lol