Gotta agree with Conan - put Vista beta on another HDD if you can. You'll still be able to dual-boot.
Having said that, here is a page that lists some free non-destructive repartitioning software -
http://www.thefreecountry.com/utilit...neditors.shtml
You might consider Ranish Partition Manager at -
http://www.ranish.com/part/
As an aside, I always keep my data on a separate
drive from the main OS - a separate partition is a second best but it might be a good use for your "lightly used" partition.