I've been playing LoR for a long time with a 32-bit XP. In this case, a Huge Map game was almost impossible to get after the Renaissance Era. In Large the problem only got annoying in the Modern Era.
I got a win 7 2GB starter 32-bit. Same issues, no good at all. The most annoying problem was the MAF (Memory Allocation Failure).
Then I upgraded my win 7 to professional 64-bit 6GB. No problems anymore. It seems MAF only happens on 32-bit OS, so change to 64-bit at once. If you have a 64-bit with only 2GB, you really need more memory to get your chariot moving like a Stealth Bomber.