Official System Requirements - Heroes 5

I bought a license, but with 512MB of RAM and a Radeon 9600SE 128MB (64-bit), it lags when zooming out and rotating the view. Will adding another 512MB of RAM help, or should I upgrade the graphics card for better quality?

Try changing the screen resolution to 800*600 and reducing the texture quality. As for the RAM, adding more would definitely be a good idea. You could then use higher settings. Although, I don't see much of a difference between the maximum and minimum texture settings; it looks good either way!