Originally Posted by jokertt
that seems the best and fastest way but it wipes all your data.I saw another method of changing the primary email but it involves a so-called ,,google apps'' app found in manage applications and selecting ,,clear data'' but so far i couldn't find it and i believe this issue is general to all gingerbread phones
??? What do you mean? It doesn't wipe ALL of your data. It wipes your contact/calendar info... because that stuff is tied to your google account. It doesn't wipe your installed apps. CarpathianUK's suggestion does exactly what you are asking about.
If you want to keep your contact info, you'll have to either copy them to your SIM card (they may be there already), or re-enter them in your contact list of the google account you want to use as your primary. I think for calendar info, you have to export your google calendar from the account you're using now, and import it to the account you want to use.
As far as the "so-called google apps" app - that isn't an app that shows up in "manage applications", per se. The Google apps is .apk that installs the market and other proprietary Google apps, like the gmail app. It exists because some ROMs (like CyanogenMod) cannot legally distribute the Google apps as part of their ROM, so they must link to the .apk externally to allow users to install them.