You might want to try expanding the volume outside of the running OS environment. Use a bootable utility like GPartEd, or slave the drive into another system. You could also use the command line diskpart.exe utility if you have a WinPE/BartPE disk.
If that fails, then you should look at capturing an image (looks like you've done that), deleting the volume, creating a larger one, and applying the image onto the larger volume. Since I'm not sure what you've used to capture the image, so I cannot say for certain whether you'll get desired results. Some disk imaging tools do a block-by-block backup of the drive/volume and will give you a partition with the same size as before when you apply it.
I generally prefer to use the ImageX utility from Microsoft to capture and apply images. This tool works on the file system level, thus allowing me to perform the partition creation and the image application processes separately. If you need to go this route and have a hard time finding the tools, PM me and I can see what I can do; it can be a somewhat in-depth process.