I Just installed MPLAB-X v1.85 and XC8 v1.20 on windows 7 with a 64 bit OS and even thou I have XC8 installed it will not use it.. And it shows up as a tool set..
Well your in luck with those chips I was playing with the samples. There for the 16F chips and I got a error that the HI- Tech compiler is not installed. Whats funny is there no way to change the project to use XC8 It's grayed out the tab to change it.
So after a day playing with it I start a new project and it ask if I want to Use Hi-tech I click the XC8 button and copy my sample code over to it and it compiles fine.
Did you per-chance uninstall MPLAB IDE v8.xxx before you installed the newer MPLAB IDE X??? Because if you did, it removes the licence registration of the 8 bit compilers...