What is your OS? Dump the OS if it is XP.

My Thinkpad T60, which is 7 years old, runs great with Win8 even with a 5400 HDD and 2GB memory.

If you are browsing, there is no reason why it should be slow.

Another thing is you need to re-install the OS to flush out any trash.

Maybe you can try OSX ... if you can hack through AMD CPU. My T60 runs on OSX fine.

Overall:

Win8 > Win7 > OSX > Vista > XP, yes, I've tried all of them. :)