Windows 7 - Add Path

I think you are editing something in the windows registry but that has no effect on the path.

Try this:

How to Add, Remove or Edit Environment variables in Windows 7

the variable of interest is the PATH

also you can type on the command line:

Set PATH=%PATH%;(your new path);

Another method that worked for me on Windows 7 that did not require administrative privileges:

Click on the Start menu, search for "environment," click "Edit environment variables for your account."

In the window that opens, select "PATH" under "User variables for username" and click the "Edit..." button. Add your new path to the end of the existing Path, separated by a semi-colon (%PATH%;C:\Python27;...;C:\NewPath). Click OK on all the windows, open a new CMD window, and test the new variable.

I founded the problem: Just insert the folder without the executable file.
so Instead of:

C:\Program Files (x86)\SumatraPDF\SumatraPDF.exe

you have to write this:

C:\Program Files (x86)\SumatraPDF\