- exe files created from 64-bit of MATLAB will run only on 64-bit Win.
- exe files created from 32-bit of MATLAB will run on 32-bit Win as well as 64-bit Win.
You need to install 32-bit version of MATLAB and recompile those files to create the 32-bit .exe file.
Note that if you don't use any MEX files (which are platform dependent) then, you can install the MATLAB Builder JA product to create .jar files. These files will be platform independent but of course your end users will have to write wrapper JAVA code to call the compiled .jar file. I'd go for the first workaround.
Disclaimer: I'm not from MathWorks Technical Support :)