I think that's how alot of people do it, I mean what other cd/dvd drive would you have? And yes some mobos allow you to boot of a usb drive such as the epia m10k but I couldn
't be sure about any other boards. And I wouldn't suggest it because it'll take alot longer to install your OS/etc... off a usb drive versus a regular ide dvd drive. And to make it your only dvd drive simply connect only that drive.