Why would you want to install Poser 5 and 7? 

Which version of windows? 

Poser shouldn't be unstable like that. Poser Pro 2010 was very, very stable for me.

I'm thinking (though I am not even close to being very knowledgeable about such things) that It's possible that an update to Windows has changed some drivers (like video drivers) somewhere. Or you've having issues with Flash/Adobe Air. Or possible IE, which I believe Poser uses for its embedded library.

Standard advice is to make sure your video drivers are updated, make sure your plugins (like Flash) are updated, don't install content runtimes into Program Files (just the bare bones main one that is automatically placed with the Poser executable when you install Poser), and make sure you've installed all the relevant service releases for your version of Poser.

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PoserPro 2014, PS CS5.5 Ext, Nikon D300. Win 8, i7-4770 @ 3.4 GHz, AMD Radeon 8570, 12 GB RAM.