After installing the SP1 RC I noted that the VGA driver would then fail?
But installing the Intel driver in safe mode or before you added the Hyper -V role would then allow Hyper-V to install fine.
0) Set Bios Virtual CPU features to on.
1) install OS
2) Instal sp1
3) Install Intel graphics driver
4) add role
5) deap breath cross fingers and when it boots get back to work ;-)