I installed Fallout 3 GOTY after Skyrim and it appears to have installed additional versions of the Microsoft Visual C++ libraries. I have multiple versions for the 2005 and 2008 editions for x86 and x64. Are all these necessary? If not how do I figure out what can be removed. Thanks.

Edit: Below is an example

Microsoft Visual C++ 2008 Redistributable - x64 9.0.30729.17
Microsoft Visual C++ 2008 Redistributable - x64 9.0.30729.6161

Don't remove them. They are there for a reason.

It seems odd though. I only need one JVM for example because it is backwards compatible.

Windows allows side-by-side installations of a number of files, mostly to get around minor incompatiblity issues between different versions of the "same" DLL. For example, if a given app code relies on certain undocumented behaviour from one of these DLLs and a bug gets fixed that changes the behaviour, the app can break badly.

Having said that, very few apps have any problems. In your case, you'll probably find that the majority of apps are "redirected" from the older DLL version to the newer one without any problems. The older version may not get used at all. However, given that it's only a few MB worth of files, it's not worth the hassle of removing them and having something break.