Sometimes, the Java file associations can become broken. Follow these steps to re-associate '.jar' files to use Java:

  1. Download a '.jar' from a sim page (Play or "Download" button)
  2. Right click the downloaded .jar file and choose "Open With...".
  3. Select "Choose another app".
  4. Check the "Always use this app to open .jar files".
  5. Click "More apps"
  6. Click "Look for another app on this PC"
  7. Select "Javaw.exe" (located here on a default installation: C:\Program Files (x86)\Java\jre1.8.0_191\bin) (note the "w" in Javaw.exe)

The '.jar' file should now open in Java.

If the sim still doesn't open, we recommend this 3rd party utility called "Jarfix":

There are two versions of Windows 8: 'RT' and 'Pro'. All of our simulations will work on a 'Pro' operating system. The 'RT' version of Windows 8 doesn't allow Java to be installed, but you can use our new HTML5 simulations or our Flash simulations. If you have the 'Pro' version of Windows 8, you can go here to install Java, and once that is finished you should be able to run all of the simulations. The two versions of Windows 8 provide very different possibilities in terms of accessibility. You can find your Windows version here. If you still encounter problems on the 'Pro' version after verifying that Java is installed, it may be that the file associations are not correctly pointing to Java to open '.jar' and '.jnlp' files. Please follow the instructions above to re-associate the files with Java.

Simulations that use sound can be unstable when run on computers using old device driver software. If you are encountering crashes or other undesirable behavior with any of our simulations that use sound, we advise updating your sound drivers, as this may solve the problem. For assistance with updating your sound drivers, contact your computer vendor or audio hardware manufacturer. Contact us at [email protected] if you continue to encounter difficulty.

Updating to the latest Java JDK may resolve the issue. Jave SE Downloads can be downloaded here