fwiw, rebooting didn't help.
So let's start playing bug report:
oh, I've figured it out (what did you expect ;-). read on.
Which version of Windows?
Windows 95 OSR 2.
By what means did you attempt to start IDLE?
What does "refuses to start" mean (error msg, system freeze, hourglass that never goes away, pops up & vanishes, nothing visible happens at all, ...)?
idle never appears.
Does Tkinter._test() work from a DOS-box Python?
yes -- but it hangs if I close it with the "x" button (same problem as I've reported earlier).
Do you have magical Tcl/Tk envars set for your own development work?
(a global PYTHONPATH setting also resulted in some interesting behaviour... on my wishlist for 2.1: an option telling Python to ignore all PYTHON* environment variables...)