Python IDLE is not starting on Windows 7

Question

I used to use Python 2.7 and then IDLE was working. I uninstalled it and installed Python 3.1.
Right now Idle cannot launch. What should i do to get it running?

NOTE

Answer 1

Once I copied the C:\Python27\tcl\tcl8.5 folder to C:\Python27\Lib as suggested in Bogdan's answer the error message "This probably means that Tcl wasn't installed properly" went away. Instead I started seeing "This probably means that tk wasn't installed properly". I had to copy the C:\Python27\tcl\tk8.5 folder to C:\Python27\Lib as well. Once I did that running idle.py from the command line in C:\Python27\Lib\idlelib was error-free.