How to install server JRE in windows7 64 bit?

OP probably already solved, but for others, I had the same problem- for some reason the file downloads as: server-jre-7u21-windows-x64.gz

When you extract it, you just get the tar file without an extension. Attempting to extract the tar (using 7-zip in my case) gives you invalid output (empty folders).

To fix, just rename the downloaded file to: server-jre-7u21-windows-x64.tar.gz

Extracting the gz then the tar should get you what you need.

AFAIK All you do is unpack it into a directory which you add to your path (the Path Environmental Variable).

I would make sure you have a utility which can untar files.