Something on your computer is preventing Exam4 from installing correctly.

The mostly likely program is your security software. In some cases AOL DataMask is the culprit and should be uninstalled. 

• First uninstall the Exam4 software you already have installed.
• Then disable your security software and re-download, then install Exam4.
• Run a practice exam.
• Re-enable your security software and try another practice exam.