Reply To: Enlarge D partition Win 7 so I can Image HD
Not knowing just how big that external HD is, or how it is partitioned at this point — but, unless your D: drive is already taking up the entire space on the HD you might be able to move some stuff from D: to somewhere else on the HD.
The Disk Manager in 7 will sometimes let you extend the size of a volume. If you are not familiar with that, if you right-click on COMPUTER in the START menu, select MANAGE, then select STORAGE, and finally DISK MANAGEMENT, it will bring that up.
Or, if you have unallocated space you might be able to create a new partition there. Then, depending upon the size of the partitions (your D:, and the new E:) you might move stuff around so there is room for that image.
As far as Win 10 goes, I had it up on a couple computers here, and went back to the original OS. One is Win 7, which is my favorite, and the other Win 8.1. I found Win 10 to be complete spyware, and offered little additional over Win 7, and in some cases much less. YMMV — try it at see what it does for you.