Not working for me...
I changed (renamed) my Live account sign in, not the account itself. But, this still meant that I had to reset my phone since you cannot change the first Live account entered. (That should be changed. And one would think that Microsoft would be tracking the account by the "unique ID", not the actual text of the account name.) Once the phone came back up, I set it up with the new account name (which is still actually the same account). Then went to Market Place to re-download my games and it wants me to pay for the games I previously downloaded. My Live account is linked to my Xbox and that seem to have made the transition fine without me having to do anything.
So, do I have any option other than paying for my games again?
Also, trying to find direct email address for Windows Marketplace Support has proven fruitless as well.