I've just register my gmail id in google marketplace and when I want to change it to other gmail it ask to format the phone, there must be a better way, no?

I only want to use 1 gmail account, the problem is when the 1st time I click on marketplace, it ask for me to register 1 gmail a/c later I want to change to another account but it won't allow unless we format it.

That's where it ask me to format the phone!

so far, I am able to sync my Outlook server email and Outlook calendar using the bundle software, the only thing left now is task, how do I sync my Outlook tasks to SGA?