CUCM Business Edition

I've tried installing BE 6.x 7.x 8.x on an MCS-7825-I3 (IBM x306, P4 3GHz, 72GB HDD, 2GB RAM) but the option for BE is always unavailable. Have bumped the RAM to 4GB and HDD to 120GB to no avail. Regular CUCM installs ok, have not tried Unity Connection, but no joy with BE. BE installs in VMware ok.

Are there any special hardware requirements above normal CUCM that BE requires?