If you're still on Parallels 9 you can get Windows 10 to run fine if you install the prl-tools-win.iso from Parallels 10. Instructions on how to manually install Parallels Tools are here: http://kb.parallels.com/en/112609 In my case I have one machine running Parallels 10 and another that is still on Parallels 9. Given Parallels license only let's you activate Parallels on 1 machine (lame IMO compared to VMWare) and I wasn't wanting to upgrade that installation just to get Windows 10 working correctly I used the Parallels tools from P10. After installing them I got the correct video drivers, etc. and everything is working fine.
