can you upgrade prem 11 to professional 11

when i check the nuance site it only states you can upgrade to prof 11 from preferred (which is dns 10)

can anyone provide me with a link to explain or ? 

Toshiba 3.0ghz intel pent 4 with HT and 2 gb ddr sdram running xp pro media center sp3 and dragon preferred 10.1   Also.....
Macbook Pro osx10.5.8 with Parallels 4.0 xp pro sp3 and dragon Pro 10.1 Intel core 2 duo 9200 i think...both have built in sound cards, toshiba is realtek and not sure about mac....using a vxi talkpro 100 headset

I use dns 10 pro on macbook and dns 10 pref on toshiba

Thank you for all of your time and effort on my and others behalf

     mawdem@Hotmail.com