Chinese gibberish in a desktop program
Any idea why this is?


This is called Mojibake, or in Chinese, Luan Ma (乱码). This is most likely due to language code mismatch -- Each character in the computer is represented by a number, and your computer doesn't agree which number represent which Chinese character with the program. 

Specifically, the Chinese program is probably in GB, while it is being opened as Unicode.


  What (if anything) can I do to fix this? 


While it is an open question to identify language codes reliably in general, since we know it is GB, there are several options:


To do it for all programs, search "region" in control panel. Go to "Administrative - Language for non-Unicode programs" and change it to the Chinese region you're in.
If the problem persists (which means Windows failed to detect the program is not in Unicode), or you prefer to set language program-by-program (because this happens to many Japanese programs as well, hence the name Mojibake), you can use Locale Emulator.