Try going
Here[
^]and find the .ISO you want to use.
If you want the Professional version though, you have to pay for it. The subscription service is where you can download older versions or others, which depends on your subscription level. You can find more info about it
HERE[
^]
The Professional version of Visual Studio 2010 includes a subscription service, but I'm not sure which one. Most of their MSDN downloads are through Microsoft's TechNet, but I'm not 100% sure if they won't give you another option when buying.
Hope this helps.
Steve