You may have noticed the released version of Windows Defender will not load on Windows 2000. Although Defender during the Beta did in fact install on Windows 2000 Microsoft put in a version check in the installer found in the release version which checks for Windows XP or above. Nice thing is Microsoft also has the tools for removing that check.

First off get Windows Defender and save it somewhere you can access it. Second go get Orca which is in MSI SDK and most likely you'll need GDI+ (all links posted below).

Go ahead and install the SDK, you can limit the install to just the parts needed if you want, Microsoft Windows Installer SDK is all we want. Once that is installed go to \Program Files\Microsoft Platform SDK\Bin and run the Orca installer.

Now run Orca and load your copy of Windows Defender and find <Launch Condition> and you should see on the right "VersionNT > 500". Highlight, right click and Cut. Save your new Windows 2000 friendly Defender.

You may find on launching Defender it complains about needing "GDI+". Thank Microsoft again for providing not only the tools but the KB on how to do this. Basically unzip and copy the Gdiplus.dll to %systemroot%\System32 folder. http://support.microsoft.com/kb/915052.

You should at this point end up with a Windows Defender that will install on Windows 2000 and considering Microsoft has provided the tools and instructions for making the required edits I find it very hard for them to come back with any legal issues in doing this. Unless Microsoft edits the license to specifically say you are not allowed to run Defender on anything but Windows XP, 2003 or Vista I don't see where they would have a leg to stand on but then again I'm not a lawyer nor do I pretend to play one on TV so proceed as you see fit.

Windows Defender Download:

Download details- Windows® Defender

Microsoft MSI SDK (Orca):

http://www.microsoft.com/downloads/details.aspx?FamilyId=A55B6B43-E24F-4EA3-A93E-40C0EC4F68E5&displaylang=en

Microsoft GDI+:

http://www.microsoft.com/downloads/details.aspx?familyid=6a63ab9c-df12-4d41-933c-be590feaa05a&displaylang=en

Related KB's:

Error message when you try to install Defender, "This software requires GDI+" http://support.microsoft.com/kb/915052

How to use Orca to edit MSI Files. http://support.microsoft.com/?kbid=255905