While we are sympathetic to your problem, there are LEGAL considerations to be taken into account when considering decompilation of an application.
Since you do not seem to have the actual Source code files (PRG, SCX, etc. files), we have to question if you actually own the Source code and/or the Rights to the Source code for the application.
Perhaps, knowingly or not, you only purchased the rights to Run the application code that was developed elsewhere.
If you do not own the Source code, we, as developers ourselves who don't want to see OUR own applications 'hacked', are reluctant to consider assisting your 'Hack' of the code that you might not have sufficient Legal Rights to.
Have you contacted the developers of the application?
Alternatively, since this seems to be an OLD version of Foxpro code (FoxPro 2.6 for Windows), you might want to consider completely re-developing it from scratch in a current version of Visual Foxpro 9 or some other language - thereby ensuring that you indeed Own the Source code as well as the ability to Run it.
Good Luck,
JRB-Bldr