Computor reboots writing to DVD

I have Nero 7 and I have an ISO made on my virtual drive that I now want to burn to a DVD. I close the DVD RW drive and after hanging for minutes the computor reboots, sent a report Microsoft who have no answer. It would seem that Nere cannot see the DVD disk in the drive as it keeps say awiting the drive, or similar.
This problem happens with both my drives Optorite DVD RW DD0201 and TDK CDRW 122032. It also happens whether I use DVD RW or DVD R.
I had the same problem under Nero 6 version 6.311.20 so downloaded trial copy of Nero 7, same problems.
Windows XP Pro SP2
Radeon 9200
Realtec 97
Pentium 4
2GB Ram
Hope someone can help, the place is full of coasters.
Cheers
Matthew
UK

dma enabled?

Yes!!
Cheers
Matthew

did that solve it?

No sorry I meant that dma was enabled.
I suppose that did look like a shout in triumph but regret not.
Cheers
Matthew

Are you sure that your psu has sufficient power?

How would I check that?
Cheers
Matthew