windows live achievment problems

hello there all.i am having some trouble with the windows live achievment system. when i got my brand new copy of fallout 3. i didnt make a windows live account until i had gotten to lvl 10. now i have made one i cannot get any achievements for quests that i hav done and i really dont want to have to make another profile just to get my achievements. is there any way to get fallout 3 to recognise the achivements that i have completed. any help would be greatly appreciated. thankyou