Use digital camera as data storage device

This is a problem that seems to be popping up more and more these days. After extensive internet searching, I have not even found mention of a solution.

Why can't I use a digital camera to store files other than pictures. It works on some older cameras but newer ones seem to block most file types. In my particular case when I plug my Canon EOS DIGITAL REBEL XS into a PC, I can't see documents that I know are on the SDHC card.

I'm using explorer. but only the .jpg files come up when the cameras in the Canon EOS DIGITAL REBEL XS. When I put the card(4GB SDHC) in my Linux notebook or another laptop I tried running XP, it has other files on it. I'm fairly familiar with Windows, well XP anyways. I have the camera sitting right here and I'm willing to try anything that might work. I know there's firmware hacks out there for the camera but none of them mention anything about fixing my particular problem.

The camera comes up under the control panel in the explorer folders list and does not have a drive letter assigned to it, so even undelete/recovery software I tried(NTFS undelete) can't see it. This is exactly the same thing I encountered with a Kodak easy share camera as well. There's gotta be a util out there that will bypass the cameras and just see the drive.