I personally have never heard of an internal DVD-R drive having the capability of being run as an external DVD-R drive. I researched it on TigerDirect.com and didn't find anything that could be of use to you.
My Suggestion is to buy an external DVD-R drive they aren't very expensive even Walmart Sells one.
What i would do is network the two computer together and transfer the information from the laptop to the desktop and then burn it from there.
You could even set up a remote connection and control your desktop from your laptop through Windows 7 and other programs