Yeah man, old computers are the shit. Just a simple reformat could save it for another 3 or so years of light computing. Actually, my desktop back at home is almost 6 years old and I do just about everything I do on my laptop on that as well...minus playing new games.
I bought a 500gb internal and put it in a case about two years ago and that was $160. For $160 now, you could easily get a TB (1000 GB) for that much. Black Friday had an internal TB HDD for 59.99. Ridic.
All i really use it for now is browsing the internet and doing projects on MS Office. Its more than capable of doing that so i dont really see the point of getting a new one. I dont play games on it anymore. I find that AutoCAD can put a bit of strain on it when i use it though.