how will I if the computer sales on the internet is still functioning?  

I have never seen a computer that cost only 80 bucks. It would depend on the site I seen it on whether I would buy it or not. If it is a normal computer site I might email them and ask them about it. I like getting computers to work on so I might buy it to see if I could fix it. There are so many sites to get parts for computers but I trust the ones that deal in computer parts all the time. When I am looking for a certian item I go to pricewatch.com they will find the best prices on stuff. http://www.rselby.net/installingwindows.htm
When I need help to work on anything I ask this guy and the local guy I know that works on computers all the time. The local guy I know is where I traded in a gateway computer and got this great computer for only a hundred bucks. So buy it if you think it can be worked on but don't be surprised if it isn't what you think it will be. Hope you have a great day/evening.

i suggest that u go for buying a computer online only if need be, going to a shop personally i always better.
a computer for 80$ , i dont think it is good at all, must have been a used one and i dont think it functions that well, if u are particular about buying it online, first get more details about the computer, then take ur decision.
good luck