I've used System Rescue CD quite successfully multiple times for things like this: http://www.sysresccd.org/SystemRescueCd_Homepage
Burn it to CD and boot to CD, it will come up with a prompt (I think its built off of Gentoo linux). Once you choose the keyboard layout (I think English is default) it will stop on a prompt with some text right above. It should indicate that you have to type in 'startx' or 'wizard' to start the desktop.
Once in the desktop, use gparted to move the partitions. You should be able to move the DATAPART1 partition to the right (grow to the right, then shrink from the left) moving the 19.88 GB next to the C partition. Then expand the C partition to the max allowable space. Once done, click apply and wait for it to finish.
If you haven't used gparted before, you may want to watch some videos on Youtube to get a feel for it, especially if the computer you're about to resize is the only one you have.
Usually after you're done and you reboot, Chkdsk screen comes up, this is normal.