No, I do not... I just wanted to learn more about what you had installed... There are no simple clues...
But I still do not see how much memory is actually installed... 1.87 GB cannot be right... so please humor me with a bit more detail...
Resources are usually what it stops, in my experience... Are all memory modules the same speed, etc.? Without a better understanding of memory resources, that appears to be a possibility... You should have at least 4 GB of memory on that machine for Windows 7, methinks, and if it is 3 years old, you might want to try a repair install if that Dell operating system will allow it. I am guessing on limited memory resources or some sort of corruption on the hard drive after three years.
Were it mine, I would want to change hard drives and run a clean new install... as a test of your system and of Age of Empires... even though Age of Empires is not really very demanding.
From your description, something fairly simple and routine needs to be fixed.
Be sure that wne it is installed, you still have a minimum of 18 percent free space on the hard drive...