Can you help please, computer extremely slow?

My aging computer crashed so my good friend gave me her old one. It’s actually pretty nice but runs so very slow (that’s why she upgraded) Anyway, I would love to try and improve on this one before I give up. It starts up okay, but it literally takes 6–14 minutes to open up some programs including the internet. Once they are open it speeds up quite a bit. I have done a defrag, downloaded c-cleaner and removed a couple of programs to try and speed it up. It has helped a little but not nearly enough. PLEASE keep in mind that I am very much a novice at computer technology so dumb it down for me as much as possible. :) Any suggestions would be more than welcome.