Eclipse executable launcher error: Unable to locate companion shared library

I've just encountered the same issue. The problem for me was Windows 7 default unzipper program. It has a problem when it encounters files that have a deep file structure. I read about this issue some time ago but can't recall the article. Fix for me is to unzip the Eclipse download using WinZip (or some other tool which does'nt have this issue).

That sounds pretty bad and weird. But reinstalling isn't that hard - download, unzip, change the default memory allocation, run Eclipse, install necessary plugins and features.

And almost all of the important preferences are in your workspace. The only important one I can think of outside of the workspace is the aforementioned memory allocation, which you can set on the command line or in the ECLIPSE.INI file.