you'll need to let your os know where to find the jre. as long as you're running your app in your IDE, no problem, but if you try to run an app or jar without an IDE, and your OS doesn't know where to find your jre, it won't run.
I have a similar problem.
I used to be able to run .jar without any problems, but ever since I installed the Nokia PC suite, I can't run my .jar-s.
The suite automatically associated itself with the .jar-s, so I re-associated them with javaw.exe (found in C:\Program files (x86)\Java\jre7\bin\javaw.exe).
That did not help, as now when I double click, all I get is a split second of that windows loading circle on my cursor and my PC is like "Meh, like I care."
Running Windows 7 Ultimate 64 bit.
I can perfectly run it through CMD (java -jar <filename>.jar).