there has been lots of threads / posts complaining about problems with flashing on windoz 7 64-bit, so you may need to use another PC.

i flashed on windoz 32, and all what i needed is to keep connecting with the net because it was always searching for the drivers via "windoz update"

as for the forgotten lock code please read this thread
http://talk.maemo.org/showthread.php?t=37808
you can get it easily