Do I know you???
You can apply software filters, HQ2x is a nice one (best to stick to multiples of 320x240 to get the best out of it without distortion e.g. 640x480, 960x720 ect ect)
Instead of setting up the soft setting and having to press F7 to switch between whatever your main plugin is and the soft settings you can just grab the soft plugin from
http://www.pbernert.com/html/gpu.htm#SOFTWIN and set that up as your main plugin
Older stuff will be fine yes