Speed Internet? Speed Computer?

well, before i reformatted it was fine, after it's a bit slow, now inside my computer it is a bit dusty, whats a good way to clean everything, its an old gamming computer, and i got good amont of ram, and im not shure ho wto properly clean it, and i was woundering, whats a good way to speed it up, like programs or anything, it's jus been reformated, so not much is on it, and any good optimizers or anything, to speed my internet, like i kno you cant use more than you have, but i want to beable to use all i have and not jus partial, so any good ideas or help? thanks.