Is there any way I can make my slow laptop usable again?

I have a Dell Inspiron B120 laptop. Right now it is so slow as to be completely unusable. It takes literally four minutes to log on, and another six minutes after I click on Firefox for the browser to actually open. It’s painful.

When I first got it it worked fine, and I assume this means it could work fine again. I’ve already tried uninstalling programs that I don’t use much, and it’s still slow as molasses. (And I don’t need any programs other than word and firefox.) I don’t have anything important on it that isn’t backed up, so I’m willing to try anything.

All I really want to be able to do is use the internet on it without having to wait ages and ages.

I really don’t know anything about computers, so I’m not sure what to do…