just do this to make yur 4gb pendrive wrk perfect
Open Command Prompt -> Type the drive name say G: -> Type ATTRIB -H -R -S AUTORUN.INF -> Type EDIT AUTORUN.INF -> A new window appears; delete all the contents and click on File -> Save and click on File -> Exit
On command prompt -> Type ATTRIB +H +R +S AUTORUN.INF -> Type EXIT
This may be a bit late for this user, but others may find it usefull.
Try this - it worked for me on a different drive.
WARNING - You may lose all your data, but your drive should work.
go to this site and download the free software.