without rebooting, IDLE refuses to start, but the console window works fine...
fwiw, rebooting didn't help.
So let's start playing bug report: Which version of Windows? 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, ...)? Does Tkinter._test() work from a DOS-box Python? Do you have magical Tcl/Tk envars set for your own development work? Stuff like that.