For the benefit of others who may have the same problem, I have compiled a list of known causes and solutions for this error:

• The setup file was damaged during download as a result of a network or download manager problem. Try downloading the game again using a different network connection or download manager.
• Your computer's hard drive has a damaged area. Run the Windows error-checking utility (for Windows XP users, Open My Computer, right-click on your hard drive icon, click properties, click on the Tools tab and press the button labeled Check Now...).
• Your computer is infected by a virus, spyware, or adware, which is causing that error to be reported. You may need to take steps to have the offending malware removed from your computer.
• There have been many reports of certain security software suites (and their components) interfering with the installation or operation of other software, which results in Windows issuing that message. The two suites that we are currently aware of are Computer Associates (CA) 2007 Internet Security Suite and the AOL Safety and Security Center. If you have either of those software suites or their components, such as CA Anti-Spyware 2007, installed on your computer, you should check their support site to see if they have issued updates that will correct the problem.