Pretty much! If you are really worried, take a backup of the disk first.
Edit - just recalled something about the Vista Bootloader - a quick Google found this....
If you want to try Ubuntu, then either install a separate hard drive and remove/disconnect the Vista drive, or use a live CD version. However I'd advise against doing what you suggested until yopu have done a little more research on the subject, starting with the links in the quote. In any case Google (and Hexus) will be you friends.
This link might also help
http://www.pro-networks.org/forum/about78184.html