I used this workaround right now on my computer with windows seven. For those who want to run the program on your computer (and not to use the CAT on line, even though is the same) as follows:
1) Click on: start menu > control panel > Device Manager > any and all sound cards or sound devices (listed under sound, video, and game controllers) > Click on "Driver" tab > click "disable button; be careful to NOT click on "uninstall"; repeat steps as necessary for all sound devices
2) Locate the .exe executable file for the Kaplan
software after installation (C: program files (X86): Kap.GMATTests: Kaplan
GMAT CD Companion.exe)
3) Right click on the .exe file and click on properties at the bottom of the drag down list.
4) Click on the compatibility tab
5) Click the radio button for "Run this program in compatibility mode for:"
6) Select "Windows XP Service pack 2" from the options available from the drag down list below the above radio button just clicked.
7) Click Apply
8) Open the program and start practicing GMAT tests!! Note that after you're done using the software, you'll likely want to go back and "enable" all your sound devices in the control panel.
I found it here.