Click on the Apple button on the top left corner, and click "about this Mac".
A window with the specs of your Mac should appear.
For Windows
Type dxdiag in the search bar in the Windows menu and click dxdiag.
Click on the "Display" tab of the dxdiag window to see your graphics card information.
Fill in your PC information to see if it runs Dungeon Siege
CPU
How do I know specs like this?
GPU
RAM
2GB
4GB
8GB
16GB
32GB
System
Windows
Linux
MacOS
Confirm
Requirements
Dungeon Siege
Gas Powered Games
Minimum:
CPU: 
333 MHz or faster processor
GPU: 
8MB video card
RAM: 0.125 GB
OS: 
Microsoft® Windows® XP SP1 or newer
Homepage
Desktop Site
Fill out the specs below:
How do I know these specs?
CPU
GPU
RAM
2GB
4GB
8GB
16GB
32GB
System
Windows
Linux
MacOS
Confirm
Where do I find these specs?
For Mac
Click on the Apple button on the top left corner, and click "about this Mac".
A window with the specs of your Mac should appear.
For Windows
Type dxdiag in the search bar in the Windows menu and click dxdiag.
Click on the "Display" tab of the dxdiag window to see your graphics card information.