merge partitions on two separate physical disks?

I have windows 7 and two separate physical drives. The C drive is on first physical disk and the D drive is on the second physical disk. The C drive is almost full and I need to make the drive larger.

Is it possible expand C drive by merging its contents onto un used space onto D drive?

Years ago I believe Partition Magic 8 would do this, but Partition Magic 8 is not compatible with Windows 7.

All replies, suggestions, info welcomed!

Aaron