If you should be running a 64-bit version of Windows, you may find that an additional step is required to allow MathXpert, which is a 32-bit program, to run. If MathXpert runs fine after installing it, ignore this message. Otherwise there are two approaches, one thoroughly tested and one newly discovered by a student, but maybe simpler.

The tested approach involves telling Windows that the program is "compatible", whatever that means. The instructions for doing that vary from one version of Windows to another, unfortunately.

For 64-bit Windows 7: right-click the MathXpert icon in the Start
menu, and pick the Compatibility Troubleshooter from the pop-up menu.
When the Troubleshooter is finished, it will pronounce MathXpert
"incompatible", but nevertheless, after that it will run fine.

For 64-bit Windows Vista Home: you won't see the Compatibility
Troubleshooter when you right-click, so that won't work. Instead,
using Windows Explorer (available from Start | Accessories), browse
to where mathXpert.exe is located, namely \Program
Files(x86)\HelpWithMath, then right-click mathXpert.exe and choose
Properties. Under the Compatibility tab, check boxes as shown here.
Then it should run fine.

These steps can also be used with other programs that were originally
written for 32-bit machines.

The newly-discovered approach might be simpler. The installation program installs the "Help With Math" folder under "C:\Program Files (x86)". To remedy the problem on 64-bit machines, simply move the folder "Help With Math" to "C:\Program Files". Then, of course, the icon on the desktop and presumably in the Start menu will refer to the old location and need to be fixed, which I think you can do by right-clicking them.