why are you trying to install 3.41 if you already have 3.41 on your drive ???
or is your FW a lower FW than 3.41 and you have it on a USB stick u mean???
If so; to upgrade to 3.41 fisrt download the update (which should contain a EBOOT.BIN file)
then create a folder on ur usb called "PS3" then create a folder in there called "UPDATE" (both folders MUST have CAPS) then place the eboot file inside
then try updating again and selecting storage media
p3free jailbreak review - http://psx-scene.com/forums/showthread.php?p=540476