None of this information is useful. The dimensions of your screen are irrelevant, it's the features of it such as maximum resolution. Everyone has a keyboard and mouse. You'll be much better off if you learn about at least a few of the technical terms and details of a computer.
Anyway as far as where to buy. Alienware is overpriced like Macs are. iBuyPower is one of the best places to get a decent PC without a lot of hassle. If you want to learn more about the innards of computers and put one together yourself (it's really not that hard after you do a little research), go for newegg.com.
