I can run .jar files through cmd, but I cannot double click them

If you don't care too much about understanding the underlying problem, this might help:

http://johann.loefflmann.net/en/software/jarfix/index.html

--and a double-clickable .jar needs to have Main-Class correctly set in MANIFEST.MF

Just to reiterate - Meghan's answer fixed my problem of not being able to double-click to start a jar in Windows 7.

• Open Registry editor

• Navigate to HKEY_CLASSES_ROOT->jarfile->shell->open->command

• Modify (Default) to "[Path to working JRE]/bin/javaw.exe" -jar "%1" %*

• Make sure .jar files are opened by [Path to working JRE]/bin/javaw.exe by default

I had the same problem, and it turns out that the .jar file association in the registry was broken. The following steps fixed it:

• Open the Registry Editor, and navigate to HKEY_CLASSES_ROOT\jarfile\shell\open\command, and modify the value of the Default key as follows
• Replace [Location of your JRE] in "[Location of your JRE]\bin\javaw.exe" -jar "%1" %* with the root directory of your JRE installation. For example, "C:\Program Files\Java\jre7\bin\javaw.exe" -jar "%1" %*.
• Repeat the above steps for HKEY_LOCAL_MACHINE\SOFTWARE\Classes\jarfile\shell\open\command.

I have a Windows 7 machine, but I assume this would work for 32-bit environments as well.

EDIT: Fixed the path in the example - it should use the "Program Files" directory and not "Program Files (x86)".