i dont get it ...i was playing l2 at that laptop and i said hmmm why dont i format it so then i runs faster and now every time i try to run the game i get a blue screen with weird letters plz help

You mean blue screen of death?
Means that your OS has gone through a critical error, if it occurs every time you start l2, then it might be a specific part, only reinstalling or if you're good at programming somewhat, then fixing the files.