Well, I have 6.06LTS dual booted on my laptop. I have the 40g drive
split into two 20g partitions. I never did get the partition program
on the live Ubuntu disk to work however. I used "gparted" to
partion the disk, then loaded Ubuntu. I have been using this
arrangement for 6 months and am using Windows less and less. I
always use Ubuntu for work on the web.

My desktop Compaq AMD3400+ has Ubuntu on a 7g partition, working
well for web work. Note that there is a separate partition also for
Ubuntu of about 3g for working files. Within the 7g I have loaded
all the codex's for audio and video, Gimp, a large astronomy program
(Carte du Ciel), and a lot of other stuff.

For the Windows partition remember to leave room for windows to
operate, say 5 or 6g minimum.