While it is true that I do do some programming, I am certainly not a programmer in the sense of these brave souls making CHDK for us!
I'm certainly not a proficient Hex-Editor, by any means, but I was inspired to try this modification from someone who had posted making the same mod by changing "G5" to "S3" to support their S3IS (I believe his was the model)
I will try to give more detail for the method. I think any HexEditing program should be fine.
When you open the HexEditor, and then open the RawShooter.exe file, the code should be divided into two parts.
The Hex part will be lots of pairs of number/letter combinations (like 9A B0 8C 87). This is always unintelligible and best left untouched (at least in the sense of direct editing).
You should also see, though, a second column of code which looks like lots of random letters, numbers, and characters but, importantly, not in pairs. For the most part this code will also be unintelligible. But you should find that, if you quickly scroll through this code every once in a while you will come across a regular English word. This, I believe, is referred to as ASCII.
In reality, the Hex part and the ASCII part are actually two different representations of the same code. That is, for every change you make in one part, there will be a corresponding change in the other part.
Since the Hex will remain unintelligible, for this exercise we want to focus on the ASCII part. So, invoke the Search function of the Hex-Editor, and make sure you tell it to search the ASCII code. Do a search for 'PowerShot' (the caps may or may not be important, as an alternative you can search the brand 'Canon' or some of the already-supported models such as '300D' or 'Pro1').
If the search function has worked, you should be looking at the part of the code that lists the names of all the supported cameras. It seems that Pixmantec foolishly decided which RAW files RSP/RSE would support purely based on the EXIF identifier and not, say, the actual compatibility of a RAW file. Since these programs are no longer supported, we can only make newer/CHDK model cameras be supported by manually changing some of the entries for camera names.
Choose a camera from the list that you are unlikely ever to own (since making this change will now make THAT camera model incompatible with this copy of RSE/RSP) and carefully change the string to the identifier from your camera. To be extra safe, I made sure that the total length of the old camera name that I chose is exactly the same as the total camera length of the new camera name ('Canon PowerShot Pro1' = 20chars, inc spaces; 'Canon PowerShot A620' = 20 chars, inc spaces); but this may not be an essential step.
Once you have made the change, save the EXE file (you can use a new name if you like, to identify that the new version supports a new camera), and close the Hex-Editor. In fact, with this method, you can have multiple versions for multiple cameras (if you were, for some reason, to have more CHDK cameras in your arsenal than Canon cameras that RSE/RSP support from the factory).
Now, your RSE/RSP should support the DNG files from your CHDK camera. It will not support the pure CRW files, however.
Hope this helps.