I'm a little surprised it can't do 1920x1080 actually even for the age.

Are you sure it's PCI for the video card? It's much more likely to be AGP. That said you are probably more likely to get a PCI video card with an up to date chipset these days than AGP. They definitely exist in PCI.

Other option is a USB video card. No good for any kind of games but should be adequate for video. You'd need USB 2.0 for sure though.

256MB is plenty for regular 2D and video applications. Memory comes in more for 3D gaming to load textures etc into video RAM.