You will need this: http://www.sysresccd.org/Download
Download it then boot from this cd. If you have 64bit system (I assume nowdays) then choose the 64bit version in the boot menu.
After it booted up start the Xwindow system with
In the system menu you will find the Gparted application (as it was mentioned by:jschiwal already) start it.
you could expand any type of partition as you want.
After partition resize I would suggest to do an fsck on the partition as well.
You have fsck(ext23) on this rescue cd.
You must do fsck from the booted sysrescuecd not from the rebooted system otherwise you will lose data!