Pls hlp!! Problem with my dvd writer!?

[MeGadgetBoy]

I got a hp externel dvd writer a few days back... the problem is when i start burning i get an error like the device is not available and the burn process fails! It also doesn't show the properties of the blank dvd - it says - available and free space 0 bytes and file type raw!!
P.S. - I use nero software, hp writer, sony dvd-r ..
Please help!!! thnx in advance!!