my 3g usb modem keeps on disconnecting

This is drivin me mad ,1 min it'll be workin extra fast,n the next it says check ur settings ,n then other times i dont even need the 3 program 2 be running n it'll connect up from my network connection folder!!! This might sound drastic :bangheadbut i seem to be formatting + reinstallin win xp at least 3 times a week...and i know i shudnt have to but ive tried uninstalling the 3 program n reinstalling n ive tried every trouble shooter goin, plz help me sum 1 ,thanx xxxxxx:wave