when i connect pcIII with computer via usb, it doesnt power up.what can be the reason for it?

i didnt get a 9v adaptor with it but it has a white connector ,what is its purpose?

I'm not sure I follow from your post, but are you solely plugging the PCIII into your USB port and nothing else? The PCIII has to be powered by either the engine (which, if I remember correctly, has to be running) or the 9V adapter before you can communicate with it.

If you don't have the battery adapter, you could always jury-rig something with some wire and a 12V power source...

Oh, make sure you get the latest version of the software from their website; the version on the CD might be a little old.