Eventually I began using only one and then discovered I didn't have enough RAM to run the DLC.
I increased my RAM to 4GB and went back to running only one file. It worked for the most part but I noticed some textures would be missing. In one instance the handle of the lockpick was missing but came back. Then I noticed some more.
I tried to delete the files, there were four of them two .esp files and two .bsa(?) files for each HDtexturepack, and reinstall but apparently you can't delete anything from Steam. I'll leave the hate filled rant of Steam for another time and place.
According to Steam I already have the DLC eventhough I "deleted" it from the Skyrim data folder.
When I try to verify the integrity of the cache files through Steam the four old HDtexture files are reinstalled.
My questions are:
1. Should there be two files for the HDtexturepack? If not, how do I install the correct "one" I need?
2. If there are supposed to be two files were the missing textures just glitches?
3. An opinion on what quality I should play the game on (i.e. High or Ultra)? My setup is:
Windows 7 32-bit
Phenom II X4 965
GTX 550 Ti 1GB
4GB RAM