I haven't tried this with Windows 7 but it should work.
Download the free Easeus partition Master
, it says it will only work with 32bit OS. I used it with Vista 32bit and it worked great.
Due to anti-trust issues Windows disk management is limited in what it can do, normally it will expand to the right but not to the left.
Another option would be to take a backup image and then delete your Drive D, format it, then Windows should be able to make the three unallocated spaces into a new partition, then you could load your backup.
Third, delete D combine the three unallocated spaces and re-install the OS.
I would use Easeus and you won't lose anything, it's fast and easy.