NEC-4550A prob....freezes when powered.

OK, this problem is annoying the pants out of me.

Just received my NEC-4550A from Scan earlier. Plugged it in as standard, as per usual. My PC fails to boot if it is in and powered...just hangs at the WinXP scrolling loadup screen.
Unpower it (i.e. take it out), everything is fine.

I boot it up without it powered...fine. Get into windows, plug it back in, the "My Computer" freezes...

When plugged in, at first bios didn't detect it....my fault, tho, both DVDrom and the 4550A were set as Master...now the rom is slave and 4550 master. Although when both master, it was fine with the previous 1300a writer.

Anyone know whats the prob? Surely if drivers, WinXP should detect it? Can't even update the driver since the pc goes mental when powered.

Any help would be great...thanks