Here's what I would do (but this means that you'll have to do most of your own tech support):
$1,000 CAD is about $650 USD, right?
Buy a case, power supply, motherboard (MSI, of course), AMD Athlon XP CPU (in the 2400+ range), 1 GB of DDR RAM, a SoundBlaster Live! 5.1 sound card and an nVidia GeForce FX video card. Get the best and fastest that you can find.
Strip the hard drive, network card, ODDs and FDDs out of your old computer. Build yourself a whole new machine. Use your existing peripherals (monitor, keyboard, mouse, etc.)
You won't have to (although you probably should) reinstall the OS and software on the HDD since you're moving it instead of buying a whole new one. I say you
should reinstall the OS because when you change chipsets, it's usually a good idea to reinstall the OS, although it's not always necessary. Still, this would give you some time to back up your data before a format>reinstall.
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ockets checks from nVidia, AMD, MSI and Creative::