Why my old mac (late 2006 ) still running so slow

hello everybody

i have a problem with my old mac book(late 2006) ,the first owner told me , he changed the memory card few years ago , but few months ago i hit it so my hard disc was broken so i also had to change it , then by the way wanted to optimise my old mac book deleting no useful application and emptying the Trash , deleting the log items , it doesn´t reopen the windows log back in , and other tricks for get fix it .

but still it remains very slow , what else can I do or change components for going more fast .

thank you guys