I use Mint 13 and I have this python script that requires python v2.6 (the default version is 2.7.3). So I go download the v2.6 source, compile and install it and the script works fine. But it messed up the 2.7 version so now I can't run default advanced mintMenu, I can't run the "mintupdate" command so the update manager doesn't work, I can't run the "mintdesktop" command, I can't run the Software Manager that uses the "mintinstall" command, and a bunch of other stuff. I read later that you were supposed to you the "make altinstall" command on secondary python version and use "make install" on the version you want to be your primary version so I downloaded the v2.7.3 source and used "make install" and then I used "make altinstall" on the v2.6, but it still didn't fix the problem.

Does anyone know what I can do to fix the problem? Any help will be appreciated.

Try if you can reinstall Python 2.7. Open a terminal and run the following command. You will be asked to type your password; note that the terminal does not give you any feedback as your type it. Share any errors of the command here. You can copy text to/from the terminal, see its Edit menu.

I've already done that. I've reinstalled Python and a bunch of other stuff related to python but doesn't change anything.

Okay, what does this say:
And can you share the output of:

It says that its version 2.7.3.

The output of ls -l /usr/bin/python* is:

lrwxrwxrwx 1 root root 9 Apr 17 2012 /usr/bin/python -> python2.7
lrwxrwxrwx 1 root root 9 Apr 17 2012 /usr/bin/python2 -> python2.7
-rwxr-xr-x 1 root root 2799288 Aug 1 2012 /usr/bin/python2.7
-rwxr-xr-x 1 root root 1652 Aug 1 2012 /usr/bin/python2.7-config