You have to set up the VM to a 64 bit OS. For example, in the OS-type settings you can go for Arch Linux
and Arch Linux 64 bit
, go for the 64 bit.
also have a question about 64 bit processor that What is exactly 64 in 64 bit architecture... it it size of data bus or something else....i know that 64 bit can machine can have 2^64 address spaces and larger RAM but don't know exact thing
The address space of 2^64 is currently not supported by any processor with AMD64/EM64T-architecture, so this is hypothetically. The 64 bit in your processor are the size of the integer registers.
That doesn't matter at all, as long as the CPU supports hardware-virtualization. The Turion X2 RM-70 does.