First of all you need the disk image and appropriate linux kernel. Then download QEMU for Windows. Unzip the QEMU somewhere. Copy the the disk image debian6-17-02-2012.img and the kernel zImage_3.1.9 into the directory with unpacked QEMU. Then open shell/cmd and run:
bin\qemu-system-arm.exe -M versatilepb -cpu arm1136-r2 -hda debian6-17-02-2012.img -kernel zImage_3.1.9 -m 192 -append "root=/dev/sda2"
Be patient because it could take few minutes to get even to the login phase. Login/password is pi/suse. After you log in run “startx” to enter the graphical environment. That’s it!
Similar procedure is possible for Linux as well. In Ubuntu you need qemu-kvm-extras package which contains qemu-system-arm executable.