You can use a "virtualization" tool to launch two sessions of the same application. It's ca program that can be used to test EXECUTABLE files without infecting or affecting the performance of your PC. Access the application's page, download and install it. Then with the ACDSee Free 1.1 installed, right click it and choose Run Sandboxed.
Note: Keep in mind that any changes you save in the Sandboxie interface are lost when you close the program.