Check for two cpu flags. vmx and lm

# this command will list all the flags 
# and highlight vmx and/or lm in colour (--color) if found.
grep -E --color '^flags|vmx|lm' /proc/cpuinfo

As you can see from this screen shot my old P4 doesn't support either Virtualization (vmx) or 64bit (lm - longmode) sigh... Grrrr.

Intel calls the Virtualization capability VT and AMD calls it AMD-V.