If you click here it may throw some light on the nature of the files.
From the short description there, it seems the files are related to the HP bundled software's thumbnail views.
I know that in XP itself, its thumbnail views create files called thumbs.db which act as a sort of cache, for faster loading of the thumbnail views. These files appear in every pictures folder where the view is enabled. In XP you can edit the registry to change the thumbnail cache settings, or even disable it. [In XP, if you disable the cache, the thumbnail views will come on a bit more slowly.]
It may be that HP uses a similar idea (there is thb in the file name - probably standing for thumbnail - why they're all called 07 I have no idea).
Further down the page on the link above, these thumbnail files seem to be related to HP's Instant Share as well. That's why if you do a search for hpothb07 on the web, you see a lot of pictures with that name.
I think the files are legitimate, and get updated from time to time when you use HP's software. As you have found, they'll just come back after deletion. I don't know if there's an option in the software to disable creating the files, but they seem at least to serve a purpose.
I hope this removes at least part of the irritation.