The most common reason for this message seems to be unzipping the eclipse zip file wrongly (for instance unzipping without recreating the directory structure). Therefore please unzip the zipped Eclipse again with a good unzip tool (like 7-zip) and make sure that the necessary sub directories are created during the extraction.
Also make sure that the path to the unzipped Eclipse does not get very long. I've seen cases where Eclipse was unzipped into a deeply nested directory structure (to put it at some place into an SVN repository) and that led to the same error message.
If that still doesn't work, you may try launching eclipse.exe with administrative rights. That should not really be necessary, but maybe your access rights are somehow broken after the re-installation of Windows.