Most existing 16-bit and MS-DOS-based programs were originally written for Windows 3.0 or Windows 3.1. Windows 7 runs these older programs using a virtual machine that mimics the 386-enhanced mode used by Windows 3.0 and Windows 3.1. Unlike on other recent releases of Windows, on Windows 7 each 16-bit and MS-DOS-based application runs as a thread within a single virtual machine. This means that if you run multiple 16-bit and MS-DOS-based applications, they all share a common memory space. Unfortunately, if one of these applications hangs or crashes, it usually means the others will as well.

You can help prevent one 16-bit or MS-DOS-based application from causing others to hang or crash by running it in a separate memory space. To do this, follow these steps:
1. Right-click the program's shortcut icon and then click Properties. (If the program doesn't have a shortcut, create one, and then open the shortcut's Properties dialog box.)
2. On the Shortcut tab, click the Advanced button. This displays the Advanced Properties dialog box.
3. Select the Run In Separate Memory Space check box.
4. Click OK twice to close all open dialog boxes and save the changes.

NOTE: Running a program in a separate memory space uses additional memory. However, you'll usually find that the program is more responsive. Another added benefit is that you are able to run multiple instances of the program--as long as all the instances are running in separate memory spaces.