Depending on where you live, quite often there are computers that are newer than your model that can be had for $50 - $100. In my area, a major metropolitan area, this is very true.
Then, you can build / replace components much easier and cheaper. Just be patient, know what you are looking for and you will succeed.
I got a free desktop due to a bad motherboard. After a couple of weeks of searching around for compatibility of the RAM and CPU, I found a $50 motherboard at Frys and now have a nice "new" computer.