If you have a PC that can run 64-bit programs, you could download the latest "With JRE" version of Data Modeler 4.0 from OTN
(This actually includes a 64-bit JDK.)
But to run Data Modeler 4.0 in 32 bit mode, you will need to provide a 32-bit JDK.
Or alternatively you could download the "With JRE" version of Data Modeler 3.3 from OTN
which includes a 32-bit JDK. However if you do this you will be missing out on the new features and bug fixes in Data Modeler version 4.0.