I have that dancemat. Yes, you can use it on pc (it works pretty well), but you need a PS2/USB adapter with the DDR MODE or you'll be unable to use combinations like
up+down
left+right
ecc..
Didn't understood your post... however to use that on a pc you need an adapter (not expensive, don't worry)
I use the "Power games" adapter 3 in 1 (ps2 to usb-xbox-gamecube) and it works really well.