The videos are fine on the PB but not on PC ? For me they play fine with the windows 7 media player. What media player and what version of windows are you using? Maybe something went wacky in the transfer. Try plugging in the usb and playing the files right off the PB .
Preferred method : do a media sync with BB Desktop software (allows you either to delete automatically from the PB after being copied on your PC; saves tons of Mb !) and then play locally on the PC.