how to pimp my deskop :))

Hello there... I have just got a new Screen recently, so now i am trying to pimp it somehow.. (cos i am bored btw). I downloaded some 1337 wallpaper but it is wasnt perfect so i downloaded vista transformator or smthn and installed it... All what has it done was, that my comp was like 5 times slower and instead of my old sand clocks there was some random circle :/
So if you guys have any usefull tips how to make my deskop nicer.. dont be shy...
Danke sehr