Windows has to install things on the first drive it sees in the system (usually the primary master). As filmmaker said, the answer to your question depends on your setup. If you want to keep your 80gb as your primary drive (maybe you have another OS or something on it), you can use boot manager programs to "hide" that partition from windows so it won't know it's there. If your 80gb is just for data, then the easiest thing to do is just make sure the 27gb is setup as your primary master and your 80gb is some other drive.