How can I virtualize an ARM machine in Windows?

As pointed Geoffroy, you can't virtualize ARM, but you can emulate it. You can try QEMU - generic and open source machine emulator and virtualizer.

I've found this!

http://sourceforge.net/projects/rpiqemuwindows/files/latest/download

It's an image with Raspberry Pi with QEMU. You only have to double click on run.bat and follow instructions.

Runs perfect.

Thanks for your answers!

Use this emulator from Microsoft - http://www.microsoft.com/en-us/download/details.aspx?id=5352