Hi,
Ensure that your OS is compatible with the IE 9 and no other application is conflicting with it. In most of the cases, the problem will not be a compatibility issue with the OS, but other applications or settings which may conflict with the installation of IE9. Another reason of problems with the source from where you are trying to install the IE9 can be avoided by using proper and genuine installation procedure. Make sure that the CD or the drive containing the setup is safe and not corrupted. If you are downloading it from the Internet, make sure that the firewall settings are accordingly set. If it is a virus issue, then you can avoid it by scanning your computer for viruses using a genuine antivirus software and then you can easily install the IE9.