OK, so maybe I am just hoping it is possible but I want to make sure since I am new at this . Is it possible to install DDR2 on this mobo, and in either case what memory would you recommend?
Nope, no DDR2 (it's not worth it anyway and its just a placeholder until DDR3 is released in a year or so). You can easily check the motherboard specs here http://usa.asus.com/products/mb/socket478/p4p800se/overview.htm
If it doesn't explicitly say it supports DDR2 it doesn't, this goes for any motherboard.