1. What version of OS X are you running on that Macbook?
2. How much RAM is installed in it?
3. Do you run/install all the software updates issued by Apple?
4. When was the last time you shot compressed air through the vents?
5. What are the machine specifications? (processor speed, processor type, etc)
As for the rest of your questions, it would be difficult to come up with an answer as we have no idea what machine it is
I have a MacBook that I bought in 2006 (I think). I replaced the hard drive Feb. 2012 after getting the "blue screen of death."
In the past few months, it performs much more slowly and frequently seems to hang up after I use a command -- for example, opening an email or pasting an item. Sometimes when I am typing, it can't keep up and I get the circling pinwheel.
I am not working right now, and money is a big concern.
First I'd like to know if the advice would be to get a new Mac. Secondly, I'd be interested in finding how others sold their old ones -- Craigslist, a user group, general newspaper ad? What would be a potential price for this given that it's had one user who has treated it pretty darn well.