VFP 6 is fully compatible with VFP 5, and VFP7 is fully compatible with VFP6
you only have to recompile the project and ready to go!
There are enhancements and new instructions on VFP6 (and of course on VFP7)
are more object oriented and are better.
You can obtain more info at the online help section What is New on VFP
There are many books than you can get.
Mauricio
Be fast like the Fox
Be free like the Penguin
Se Rápido como el Zorro
Se libre como el Pingüino