The program users a 'brute force' system to obtain the key as it processes over a million combinations and characters. This process obviously takes a long time but you can pause and resume it when you want. It's best left on overnight whilst you don't need to use the computer for maximum effectiveness. However note that Windows Password Cracker is only effective in systems that use the SYSKEY Microsoft protection protocol. If yours does not, you'll be wasting your time using this although there are other password crackers available for other systems.
An efficient and comprehensive password cracker but be prepared to wait whilst it processes the millions of combinations possible.