Many thanks for your quick response.

Both the burners are external and have thier own power supplies and use USB 2.0.

I tried plugging them both directly into the computer, but the result is the same.

I have renamed the optical drives as you suggested (although I haven't been able to re-install the Memorex).

The operating system was re-built from scratch about a month ago so I assume I have the most recent USB drivers. What source would you recommend for looking for more recent USB drivers?

BTW, each works just fine if it the only one!

Thanks again,

Nitram