Actually, the 10GB install size for Vista means it won't ever get close to my hard-drive, until I get a bigger one. Currently I have a 120G HDD, which is split 50-50 between Windows and Linux. As we all know, with time, Windows' performance degrades and even though XP does not require reinstalls as often as say, 98 did, it still needs it occasionally. About a year ago, I decided it was time to stop doing an hour-and-a-half* reinstalls and simply repartitioned the Windows space into a 5G C partition and 55G D partition. Windows, firewall, anti-virus, anti-spyware, firefox and a couple of others go on C and there is still about 700MB left for the swapfile. After I completed installing the aforementioned software, I took and image of the drive under Linux and the next reinstall took about 15 minutes. I could cross my fingers/make a backup and use Partition Magic or similar to enlarge C and lessen D, but I don't think Vista is worth it.
*XP takes about 30 minutes to an hour. Then there are all the essentials, such as anti-virus, anti-spyware, drivers, firefox and other much needed programs.