Why Is My Computer Running Slow

I don’t want to pay for anything, but i know there are a ton of free software out there. What can i use? My computer runs slow a lot. But other times it will work fine.
Also, there are a lot of unused and unwanted programs i have, that i think i deleted in control panel, but the icons are still on my desktop.
I have PC, windows 98 XP home edition.

I lost the game though, so unless I were to buy another one I couldn’t reinstall it. I don’t know if I will ever feel like playing it again. and it makes my computer pretty slow. Help!?