Please check this tutorial: Partition Wizard : Use the Bootable CD
Partition Wizard is an excellent free utility that will solve your problem, no ifs and no buts.
All you need to do is download the Partition Wizard ISO and burn it to a blank CD then boot into it and carry out any partitioning options you require.
When you've done that you just boot back into Windows. As you've discovered, Windows Disk Management is very basic in what you can do with it.
As ever, backup any data you don't want to lose before you start.