Windows 7 operating system is not listed under Microsoft operating systems in VMware 6.5.1. You can upgrade the latest VMware workstation by visiting VMware site. This article explains How you can Install Windows 7 64Bit on VMware 6.5.1 workstation without any upgrading.
Even if you have 32Bit Host operating system, installing windows 7 64bit in VMware is possible if processor supports 64 bit architecture. Read more about how to install 64Bit guest OS in 32Bit host OS.
Once confirm your processor supports 64bit architecture, select the Windows Vista x64 Edition from Microsoft operating systems while selecting the guest operating system.
Other steps are normal like installing windows operating system. Good thing is, Windows Vista 64 Bit VMware tools also can be installed in Windows 7 64Bit guest operating system in VMware 6.5.1.
Enjoy with Windows 7 64Bit in 32Bit VMware.
