...Windows smartphone 2003 without problems?

that would be more of a question for moto not us to even see what the min requirements are of the OS and what you phone has
off hand i don't know but i bet someone could shed some light on the subject or atleast point you in the right direction

No official version of Windows Mobile 2003 was ever released for the MPX200.There's an unofficial version running around the Web but since you asked about whether you could do it without problems ... there would be no support with an unofficial version and you could end up with a brick.

www.mobilegadgetnews.com

Not neccessarily without problems, but you can find roms on the internet to upgrade that particular model. But honestly, the MPx220 is affordable on Ebay now. You may want to go that route. Otherwise the roms are out there and the instructions are usually included.