In the %REP_HOME%\Rep Attack 11g XE directory, double click on the VirtualBox installer file called VirtualBox-<version>-Win.exe, and follow the instructions. You will need Administrator privilege on your computer to install VirtualBox.
The example shown here is installing VirtualBox 4.3.14 although version 4.3.12 is distributed with Rep Attack and works fine. The installation should only take a few minutes at most.
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Accept the default options and click Next to continue.
Click Yes to continue. Your network connections should be restored without interruption.
Click Install to start the installation.
The software files will be copied onto your machine. Click Next when complete.
When the installation has completed, click Finish and the VirtualBox Manager will start.