Dag,
I was checking out your system specs, and it doesn't look good for upgrades, but processor speed is more important for BD in your case- and memory, I think your system supports 256mb ? I would max that out first, if you haven't already. The video you have onboard is AGP- that's why you have no slot. Going with PCI is going to require a higher end card to compensate for the loss in bus speed, I suspect (this depends on the agp implementation). If it were me I would look for an GeForce FX series, maybe 5200, with 128 MB in onboard memory. Although I cannot find specs on your video performance, I am certain this technology would be an improvement for you, though whether that means an improvement in BD I can't say. Your processor speed is probably your bigger issue right now.
That card is available for about 75 dollars US, including shipping. Keep in mind that new computers that are substantially better in every way are available for ~400, so spending more than about 100 bucks american seems a bit foolish.
