17-year old Windows bug fix

Google got caught out in China, allegedly because of a bug in Internet Explorer version 6, it was a Google engineer who spotted the security bug. Now, the same engineer has found a bug in all 32-bit versions of Windows (including 7, Vista, and XP) that date back even further into the depths of ancient computer history than IE6 – 17 years back, in fact. At the time most of us were still running 16-bit applications, and using DOS programs. Because of that, Microsoft built into the Windows kernel a virtual machine that would enable the 32-bit flavors to still handle the 16-bit programs.

Today, the bug could be exploited and let a hacker run any piece of malicious code they liked on a 32-bit Windows computer without too much trouble. But, I doubt there are even as many people still running 16-bit software these days as using IE6, so isn’t it time MS deprecated, or least disabled, this virtual DOS machine by now?

Well, while we wait for the patch. The quick fix is very easy to do. First, backup your registry, then copy the following code as plain text into a text editor and save the file with a name like “VDMdisallow.reg”

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\AppCompat]
“VDMDisallowed”=dword:00000001

Now, double click the file from file explorer and let Windows incorporate it into your registry by clicking yes when the popup asks. Reboot. That’s it. You’re now running a much tighter 32-bit Windows machine that will no longer allow 16-bit applications load.

If you happened to still be running 16-bit apps, you would want to think very hard about upgrading your software. But, if you’re feeling nostalgic, here’s a site that will show you what it was like to be using Windows 17 years ago.