I also can't get Windows 7 VM to install but my problem is a little different,
My setup:
Supermicro: CSE-846E16-R1200B
Motherboard: X9DRI-LN4F+
CPU: Intel Xeon E5 2690v1 2.9Ghz x2
Memory: 192GB DDR3 SDRAM ECC (24x8GB)
Disks: 6 x WD Red 2TB Raidz1 & 1 x 128GB SSD stripe
Attempted to install VM on the SSD