Back when Microsoft Security Essentials was first released, a lot of people wondered where the version for Windows XP 64-bit was. After all, there was a version for XP 32-bit, one for Vista/Win7 32-bit and one for Vista/Win7 64-bit.

But try as they might, no-one could install MSE on WinXP 64-bit without receiving a 0x8004FF04 error claiming that the O/S was unsupported.

Recently Microsoft released Version 2 of Microsoft Security Essentials. Since I was doing a rebuild on my workstation anyways (new hardware!) I decided to give it one more whack.

Since MSE needs to install “hooks” into the operating system in order to function properly, and since XP 64-bit is a 64-bit operating system, it could not accept the 32-bit “hooks” that MSEv3 for XP 32-bit would try to install. Therefore, I tried the MSEv2 64-bit for Vista/Win7. It worked PERFECTLY.

As you can see from the image above, I am obviously running MSEv2 (since it has a grey background with a white grid on the right) on XP 64-bit.

A few days later, when I finally managed to confirm the stability of this server, I had a wild idea: why not try it on Windows Server 2008 R2? As you can see below, it worked.

How long this will last, is anyone’s guess. I am going to make the assumption that MSEv3 will most likely not work as v2 has. But for now, MSEv2 64-bit for Vista/Win7 is working just fine on my copy of XP 64-bit and my 64-bit copy of Windows Server 2008 R2.