Can't detect bootcamp partition on windows installation
I do not have VMware 6 so I can not post a direct answer to your question. I believe the reference link given in your question has left out many steps that need to be taken in order for you to succeed. There is two previous answers posted here at Ask Different where VirtualBox was used to install 64 bit Windows 7 on older Macs. The links are given below. 

Boot camp install of Windows 7 issue, no bootable devices
No bootable device USB 2.0 MacBook Pro mid 2014

VirtualBox is a free product. Since you are using OS X lion, you would have to install an older version of VirtualBox.