Ah, the old "PC's can be upgraded" argument.
It's true, but only if you upgrade them
all the time. Just for the sake of doing so. If you actually wait until you
need to upgrade, you'll be replacing...
The Graphics card.
The motherboard, because your old one isn't quick enough for the graphics card.
The CPU, because there's a new socket type.
The RAM, because DDR2 is old now.
Windows because you had the old version.
Oh look, you just bought a new PC...
Upgrading PCs reminds me of Trigger from Only Fools And Horses.
http://www.youtube.com/watch?v=pbha4XclSMU