You need to choose which browsers you are going to develop, and have virtual machines (or use services that return images on different machines) for each one you are aiming for.
MSIE 8 is no different - you should have a test bed.
As for whether it belongs to your development machine, it should depend on other factors, such as whether it helps you develop better, does not interfere with your other work / software, and whether you want this to be your goal the default is what you expect from most of your customers.
-Adam
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