I gotta say, if you are in the market for a desktop computer, write down what you want/need it to do. then do some research and buy the parts and build it yourself. you will come out with a better quality computer than what you would get from the brand names.
Laptops, there was an article a few weeks ago that did a quality comparison and they found that HP laptops were the worst, ASUS laptops were the best. And even the ASUS had somewhere around 10 percent dying after a few years. (HP had 25%)
The one thing that I have noticed on some of my old computers that have had components go bad is the common denominator is heat. bottom line, if your computer gets hot, bad things happen. make sure you have adequate cooling for the computer and adequate airflow around the computer itself.
of course that all does not matter when you leave the computer on in an upstairs bedroom in the middle of the summer and forget to turn on the A/C before going to work...
Another thing that was touched on is you get what you pay for. sure you can slap a 40 dollar motherboard and a 19 dollar powersupply and make a running computer, but you are very likely to have that computer choke and die on you too.
Just my $.02
Oh here is the article on the laptops:
http://www.electronista.com/articles/09/11/17/reliability.study.has.apple.4th.place/
Acer aint the worst, but it is down there...
again also notice that if you get the premium notebook, your chances of dying are a little better
AJ