partitioning of a system to enable installation of another distro

[10ghost]

hi friends
about 4wks ago i installed ubuntu on my system allowing it to completely wipe off my windows vista. yesterday i tried partitioning my system so that i would be able to install redhat on the new partition but the resize button on partion editor was not enabled.
how can i partiton my system so that i would be able to install redhat on the new partiton.

[Partyboi2]

Check that the partitions are unmounted first before working on them, if you are using gparted you can right click on the partition and choose to unmount.

[jflaker]

you can't partition a mounted drive. If you want to partition your main drive, you must boot from the livecd.