How to Make MineCraft Faster?

So I have a Dell Mini laptop {Windows XP} that has Windows 7 Starter pack on it. It also has Service Pack 1, and is 6 years old.
I'm trying to find out how to make MineCraft work a little faster on it. I'm not sure if its because its such an old computer, but it just lags out all the time.
I've tried almost everything, giving Java more memory, giving me more RAM, deleting tons of pictures {486 to my hard drive!}, deleting unused apps, getting the latest version of Java constantly, updating my antivirus packages, but nothing works.
I'm probably going to get a new computer soon, but I was just wondering if there's any hope for my old one.