You could press the power button on the second monitor.
Head into your System Preferences, and from there click "Displays" from the "Hardware" section. On your primary display you should see some resolution/color options (as well as on the secondary display). Click the "Arrangement" tab at the top and toward the bottom you will see a checkbox entitled "Mirror Displays". Tick this check-box and your extended-desktop will be disabled and you can simply switch the secondary screen off. Hope this helps.
Also: To help speed this process up to allow you to do this on-the-fly, head into the "Display" tab on your primary display. Check the box on the right side toward the bottom entitled "Show displays in menu bar". This will place an Icon to the left of your clock allowing you to turn mirroring on and off. From my short testing of this I have found mirroring being disabled to put some of the windows back the way I had them before switching it on, but nothing you should have an issue with since you seem to only want extended desktop some of the time (I have to have it on always or I go into a complex).
If this does not solve your particular problem, feel free to PM me about it and I will definitely attempt to find a working solution for you >.< (possibly a simple apple-script could do this).
Your wow won't work without emulation? Are you talking about WINE (or Darwine, aka CodeWeavers Crossover Mac)... I went to best buy and picked up a $1.50 trial DVD to install fresh with. When I switched to mac I intended on it being permanent so I invested nearly 5-6hrs of my time downloading the updates one by one.
I'm waiting to try a new LawlessPPC, hopefully he makes a new one for 10.5.5 with the new kernel (I know he uses a Phenom and that's the processor I'm upgrading to... his MoBo is similar to mine so he will always include support for my disc controllers, I had some problems with iDeneb and the 'still waiting for root device' message)