As for standard parts, when you buy a name brand computer, you can consider it a throwaway when the warranty runs out. You don't get a real copy of windows, and you can't install any non brand parts that will survive a reinstall. If the disk crashes you lose everything, including windows -- unless its still under warranty.When our 6 yr old Gateway crashed, our tech guys where I work not only built us a new computer, but fixed the old one, transferred all the hd data from the old to the new, and now our 7 yr old has his own computer to play games on and practice typing/word processing.
I build computers from garage sale parts. It's not hard if you have at least one complete copy of Windows. But on the bargain PCs you don't get a Windows disk.