Hyper-V Program Manager
As more people are getting computers with hardware virtualization support, an interesting problem has been observed. On some systems, enabling hardware virtualization in the BIOS will not take effect on a system reboot. Rather, these systems need to be completely turned off and then restarted before hardware virtualization is enabled.
My another observation is that sometimes putting computer to sleep disables virtualization.
These look like BIOS bugs. Please report them. Motherboard manufacturers do often provide updated BIOSes for downloads, and often don't even charge money when allowing bug reports to be submitted.