New PC has too many cores to run the (old) game

You just have to start the game with less cores.

What you do is pretty simple, but I'll walk you through the whole process so you get a nice looking solution:

First you go to the directory where the executable is

For example in Steam:

• In your Steam library right-click "Assassin's Creed" and select "Properties".
• Left-Click "Installed Files"
• Left-Click "Browse..."
• Now you are in the correct folder and can use it directly or copy/paste the path and use your normal way of doing things.

Look for the executable

Find out, which file has to get executed for your game to run. Let's say, you find out it is YourGame.exe.

Create a .cmd file

Create a file with the name "start-affinity.cmd" with this content:

start /affinity 0x0000000000000003 YourGame.exe

If this is not working, try changing the hexmask. Here is an Url which can quickly help you, but if you want to understand what you are doing then open a command line and enter:

help start

and look for "AFFINITY" to get started.

Create a new desktop icon for this new .cmd file

• With the RIGHT mouse button, drag&drop the .cmd to your desktop.
• Select "Create shortcut here".
• Rename the shortcut to "Your Game".

Changing the icon

If you are feeling fancy, change the icon of the desktop shortcut:

• Right-click the shortcut on your desktop
• Properties
• Shortcut
• "Change Icon..."
• Browse to the directory where you just created the .cmd
• Select the YourGame.exe
• Select the icon
• Ok