well i just got my dell dimension 2400 up n runnin again but there are some problems that i need help with 

1) i need a new operating system ...im pretty sure i know how to do that what with windows being designed to make computers work properly it'll problly tell me what to do but ya know my only real question in this is what would you guys recommend? or what is the latest thats not vista or could i just get a copy from a friend? <--- that may not be particularly legal but idc i just want to know if it would work if a new disk is too expensive  

2) I need internet connectability i have a working att wireless router brand new just got delivered today and i have a d link wireless reciever thing i just got from my buddy but idk where to go from there so i need some advice on how to get the internet up n running without boring holes in the floor / wall or dragging a cable 18 miles from the router to the computer so i need it to be wireless 

3) im not sure what to do with it do i just need soft ware updates or do i need hardware updates to get it up to speed with the so called "big boys even though its far larger than any laptop my goal is to have a fast running internet capable game capable and multitasking computer with which i can do whatever so pleases me at the moment with out fear of slowing down or crashin (hasn't ever before but you know how these things go)