Download and burn free Partition Wizard bootable CD
to CD with WIndows Image Burner or ImgBurn.
Boot CD, rightclick on C to Resize, drag left border all the way to the left, if desired drag the right border to make the partition the size you want, click OK, then Apply. Partition Wizard Resize Partition Video .
In the rare case where resizing on the boot sector causes Windows 7 to fail to boot, boot into PW again, click on Windows 7 HD to highlight it, from Disk tab run Rebuild MBR, click OK, Apply. Partition Wizard Rebuild MBR Video
If this fails to start Windows 7 then boot into Windows 7 DVD or System Repair Disk
to run Startup Repair up to 3 separate times with reboots until Windows 7 starts.