I tend to disagree when people say Dells are reliable. I repair Dell computers quite often, they are probably the #2 brand that I fix. Most repairs turn out to be rather expensive for the customer since parts like the psu/mobo/even memory lots of times is propritary and can only come from a few places. Constructions tends to be rather cheap and slap dash imo.
Keep in mind that Dell makes a majority of it's money with businesses rather than normal consumers. Corporations rarely purchase computers, rather they lease them for 2-4 years and then get new ones; much more cost effective this way. ANd that's all the longer Dell computers are required to last, that 2-4 years they're needed for.
But that's just my opinion from repairing so many of them...