IMHO Steve your getting the benefit of some real quality advice here....I've been going to renew my system for over two years now (even set the money aside then) but constantly found myself pondering over whether to go dual or quad core, then pondered over leaving my XP Pro for Vista (heaven forbid).
Along comes the much needed Windows 7, yet still sitting on the fence undecided.
The problem I have (if you could call it a problem that is) my 3.2GHz Athlon, XP Pro, 2GB, 900watt PSU, nVidia 7800GS (BFG lifetime warranty) AGP system runs SH3 and 4 quite happily so I have difficulty in convincing myself to part with the Pesos atm.
One day graphical requirements etc will force a system renewal but until then I'll keep what I've got thanks.
I've never believed in trying to fix something that isn't broken.
Oh and I'm on the fence regarding graphics cards, I've tried them both without any hiccups or complaints
