How do I resize boot camp partition?

I used Disk Utility to change the two partitions on my hard drive: Mac MBP HD which had 450.9 GB and a Boot Camp partition for Windows7 with 49GB.

I wanted to move 4GB to Windows7. The first of two partitioning operations went okay. Then the second operation started but it quit saying: Invalid request. Operation failed.

Disk Utility partition operation created a new, additional Untitled partition with the 4GB. The Mac HD had been reduced to 445 GB.

Where do I go from here? I looked at other, older questions/answers but they weren't helpful and may be out of date or were complicated. On-line videos were for older OS and some people who tried them didn't have good success.

My Mac MBP HD is backed up on an external disk drive. I may have to purchase another external disk drive to backup the Boot Camp Windows 7. The Windows 7 partition is too big to copy/backup to DVD disks. Any suggestions for backing up Windows 7? A disk image?

Thanks for any help.

Bonnie W