You are completely out of luck. You'll need to upgrade to a reasonably recent version of Photoshop since the first version of Camera Raw that could read DNG Converter DNG files is Photoshop CS2 using ACR version 2.4.
The best you can hope for is to process the raw files using the camera maker's software into TIFF files that can open in PS 7.
Also note that PS 7 is outside the upgrade window for CS5 (only three versions back so CS 2 is the last version that can be updated to CS5) so you are additionally hosed regarding upgrading.
Tough luck bud....better off to stay relatively recent with Photoshop upgrades.