Which Mac do you have? and did Lion come with the machine?
I have an iMac i3 3.2Ghz. Lion did NOT come with the machine, I upgraded to it.
Hopefully you're aware that you can't just install Snow Leopard in a VM directly, you have to go through a process to fool Parallels (or other VM software) into thinking you are running Snow Leopard Server, because they won't let you install an unmodified copy of Snow Leopard since it's not licensed for use in a VM.