You would have to reinstall your programs if you reinstall Windows 7.
It would be much easier to use free Partition Wizard bootable CD. Free Download Magic Partition Manager Software - Partition Wizard Online
DoubleClick on downloaded ISO file to burn to CD.
Boot PW CD, select 1 for Screen Res, rightclick D>Resize, slide left grey border to the right by as much space as you want to extend C into. Click OK.
Next rightlick C>Resize, slide right grey border to the right to take up the space you made from D, OK. Apply all steps.