Windows 7 comes with a built in partition resize tool
see
Resize a Partition for Free in Windows 7 or Vista - How-To Geek
note that you'll probably have to delete d: and then expand into the freed space. Trying to shrink d: probably wont work as it will shrink from the "top" of the partition, not the bottom
If there is any data on d:, copy it to somewhere else first
If you want to keep d: and shrink if from the bottom then you'll need third party software. Theres a couple of Linux distributions which are aimed solely at doing this, using the GPARTED program
Partedmagic
GParted -- Live CD/USB/PXE/HD
if one distro won't boot on your machine, try the other