You could just go for a dual core, try to unlock the other cores, and maybe overclock it. You'll easily have it preforming at way more than its worth.
This is assuming that it's other cores are good.
I got a AMD Phenom II x2 BE for this very reason.
I got the Antec Sonata III from newegg. It came with that PSU I believe, and was only $100 for both. It's a great case, could use another fan though.
As for the video card I would recommend this card it's a better card than the one you picked out everything else looks good.
Newegg.com - HIS H467QS1GH Radeon HD 4670 1GB 128-bit DDR3 PCI Express 2.0 x16 HDCP Ready CrossFireX Support Video Card - Desktop Graphics / Video Cards
If you are going to upgrade from windows xp to windows 7 all your drivers in you computer/laptop will be deleted so you should have the cd that came with your computer
Roger, I agree that mom probably doesn't need a quad system with DDR3 memory. Truth be known, if the OP's mom is like my mom, an old P4 system for her email and web browsing would work just fine.
But the OP said he wanted something fast, and something that will be good for a while. The core 2 duo is getting a bit old and is now 2 generations behind. I just figured a quad system would be something that will last, and won't seem like ancient technology by next Christmas.
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