I've decided to use PyQt which is more attractive Graphical User Interface (GUI) than Tkinter. I downloaded the setup file from official site, and started to install PyQt4. My all attempts were unsuccesful with ridiculous error messages. "Required Python version 2.6 did not installed on your computer" was written as an error code.
On the internet i've checked that error code and, i found this mail list. Somebody faced the same problem and he or she stoped working with PyQt beacuse of same silly problem.
I've changed the PATH, uninstalled and re-installed the PyQt again and again, but nothing was changed. At the end i've removed the Python2.6.4 (64bit) and instead of 64bit i've downloaded and installed Python2.6.4(32bit). After this substitution everything is working properly now.
If you have 64bit Windows and 64bit Python too and also use PyQt, please explain me your solution.