[Q] default gallery settings problem

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http://forum.xda-developers.com – hey guyz. i wanted to change the wallpaper on my xperia x10. so i touched and hold down on the screen. then, clicked wallpapers and then clicked on gallery. after that 4 options appeared: Astro File Manager, File Manager, Gallery and Office Suite. by mistake i clicked on Office suite :(:(. and it was selected as default setting. now whenever i click on gallery while changing wallpaper the Office suite appears. :( not only this, i downloaded a photo editor app. when i try to select gallery from the app to edit photo, there also appears as Office suite. now plz plz plz tell me how can i fix (HowTos)