I finally fumbled my way through solving the PC half of this one. I'm not sure the techie terms involved or all of the explanations behind how this works but I can at least post how I was able to fix it. At least if I royally goof something up I can come back here and retrace my steps.
First there were two problems to address, hardware and software. Hardware was a combination of the SDHC card had unallocated space and the card reader on my desktop did not support SDHC. The software part was much more complicated as there wasn't a one-size-fits-all solution to the problem. I had to download updates and another software program to get this part fixed.
So here's how I did it:
1) Buy a USB card reader that is SDHC compatible.
2) Update the card reader firmware for the desktop computer. For mine I did not have any success with Microsoft (some people did) while I had to go back to HP for the file. In case anyone else has a HP, do a search for file sp38607.
3) Try to format the drive through Windows Explorer and see it's only recognizing 3.7GB. Open Disk Manager and see there is unallocated space and Disk Manager doesn't fix this. Go oh S#*!.
4) Find Fat32Formatter and allocate the other half of the card. (Something about XP can't handle the larger formats???)
5) Discover Fat32 Formatter allocated the card but not formatted.
6) On a hunch, go back to Windows Explorer and try to format again. It recognizes the card is 8GB (YAY!!). Format as Fat32.
7) Transfer files and install micro SDHC card in the PDN.
Now to figure out why the PDN still isn't recognizing the full 8GB on the micro SDHC card. Grrr.
Edited to add: From what I'm finding is the larger cards automatically lose half the volume. Not sure why but it would have been nice to know this before I bought the 8GB card.