Just install without a key.
After 60days of free usage u can do this:

Start Command Promt with admin privileges and enter:

sysprep /generalize
slmgr.vbs -rearm
rundll32 slc.dll,SLReArmWindows
slmgr /rearm

REBOOT

This will give you another 60days. Will work 3 times = 240days.

Until then there will be a solution for that "problem".