Is this for Windows Virtual PC? If so, you can visit the site for that program. There's a scanner to determine if you can do it or not, and if you can, if it's enabled or not. There's a set of instructions for each brand, you'll have to comb the site carefully to find the instructions. It involves going into your BIOS, the procedure takes a couple of minutes. It takes longer finding everything than actually doing it. There's other VM's that doesn't require this, XP Mode from Microsoft doesn't require it anymore. And Welcome to the forum, alex66! I just noticed this is your first post. If you need anymore help with this, feel free to post back, or if you have any other issues, do the same. I have 5 VM's, but only one of them required the setting, but it's changed since then. But one thing, XP Mode from Microsoft requires you to have Windows 7 Pro or above. They claim it's for small businesses to adapt, I say that it's a money issue.