One of the reasons why PC sales have slumped, at least in my opinion, is the fact that many users do not see the need to upgrade their systems as often as before.

Back in the days, upgrading the processor from a 486 to a Pentium, or a Pentium to a Pentium II, was a huge deal, as were upgrades to system RAM (128 Megabyte for the win), or the video card.

Today, upgrades do not yield those high performance gains anymore. Sure, it is nice if you install a new video card to get even more frame rates out of games you play, or a faster processor to convert those media files faster, but all in all, the gains are not as noticeable as before unless you are updating a very old system.