If I understood you correctly, you are simply looking for a way to use an XSLT processor without having to use IIS (or another web server with added support for this feature).
There are quite a few ways you can test XSLT transformations without having to install any software at all. A ton of different web pages will transform XML for you (given your XSLT and target XML). To name a few:
- http://www.xmlper.com/
- http://www.online-toolz.com/tools/xslt-transformation.php
These online tools, though, normally utilize processors that conform to the XSLT 1.0 standard. This means that if you're planning on using XPath functions/other such rich features, you'll be better of downloading an IDE that specifically supports XSLT 2.0 transformations.
Commercial products include Visual Studio, Altova's XML Spy etc.
I'm not too familiar with freeware products in this case, but I think you can also try using Netbeans IDE with the "XML tools plugin". (In case of using Netbeans: if you need XSLT 2.0 support, you will probably have to configure it to use a Saxon processor(supports XSLT2.0) instead of the default Xalan processor(supports XSLT1.0)).
EDIT: As Ignacio pointed out, there's obviously a plethora of ways to transform XSLT using command-line tools. My aim in this answer was at visual transformators, as I find these to be more beginner-friendly.