First of all welcome to the forum.
I think that your PC/laptop is a bit underpowered for battles in RTW. It only has 64MB of memory on the integrasted chip(?).
What graphic settings are you trying to use on the battle map (unit size, resolution and other settings)?
Edited: Basically the graphic settings from the following screen (it's from a mod as I don't play vanilla RTW) (from the Options Menu):
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