UPDATE:
Please note that Microsoft no longer supports Windows 98 or Windows ME
(Millennium). Some of the Microsoft links may no longer be accessible.
Although the package might list these Windows as Supported platforms, 
Turtle Beach does not support them anymore.
From Microsoft Website: 
http://www.microsoft.com/windows/support/endofsupport.mspx

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IMPORTANT!  You may see a message explaining that the software has not passed
Windows Logo testing or does not have a Digital Signature.  This means that we
have not had Microsoft test our current driver version and certify it as
Windows Logo compliant. 

However, the driver and software have undergone extensive testing under all
supported operating systems so you can safely install the product. This will
NOT make your system unstable. 

Under Windows ME - it is critical that you follow these steps:

1.  When the following dialog appears, click on the Advanced button:
    

2.  Then, select 'Warn when installing unsigned devices' and click 'ok'
    

3.  The final step is to select 'Yes' to continue the installation then 
    click 'ok'.
    
    At this point, installation will continue normally.

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