If you take the PCNAME of the Laptop with the DVD Drive, (this can be found by right-clicking My Computer, selecting properties, and browsing to the Computer Name Tab).

Next, right-click on the DVD Drive, and select properties, go to the sharing tab, and select share this folder, and type in a share name such as "DVD"

On the other PC, (assuming it is the same as Windows, and they are networked together), go Start > Run and type

\\PCNAME\DVD

It will ask for username and password of the laptop

In My Computer in Windows you can select "Map Network Drive" in the tools menu, and use that text to map it permanently, what you can do in Unbuntu I don't know.