i installed my windows 7 beta on a separate partition. as long as u select custom install, and install it to that partition, it should be fine. The only thing to be careful of is that some installs of vista also have a Recovery drive. If you end with 3 partitions, (so far) I have not gotten 3 partitions to be recognized, and so my main drive does not show up on windows 7. But I highly recommend the separate partition, in case something bad happens.