Hi folks !

Just DL a file with a .SIT extension ???
What to do next ??? - I tryed to rename to zip, rar & exe. No luck

It's a compressed archive. If you don't have a Mac, you're out of luck. Chances are, the file inside it will be something you can't use on your PC anyway.

It's a Stuffit archive. Commonly used on Macs, though there are versions for Windows, Linux and Solaris (see http://www.stuffit.com/). But as bink says, the contents might (or might not) be Mac-specific anyway.

Just the information I was looking for re "sit" files. But, is there any way to tell if a particular file will work on a PC rather than a MAC?

Try it and see!  In general, applications and other executables will not work*, but data files might, if you have a Windows app to load them into (e.g. plain text files, pictures, audio files, Word documents, etc.)
<p>
There are a couple of complicating factors (warning &ndash; techie bit!):
<ul><li>Filename extensions.&nbsp; Mac filenames may or may not have a three-character extension telling you what they are.&nbsp; Older versions of Mac OS (9 or less) completely ignore any extension, and use special Mac-only 4-character codes called the CREATOR and TYPE, stored with the file, to work out what it is and what to open it with.&nbsp; Mac OS X can use either extensions and/or TYPE and CREATOR codes, just to confuse the issue further.&nbsp; And many Mac users use an extension for cross-platform files just out of habit, anyway.&nbsp; So: if you see a file without an extension, it may be a file you could use if you guess the right extension to rename it it, or it may be something you can't use at all.
<li>Resource forks.&nbsp; Unlike Windows/DOS/Unix files, which are just a sequence of bytes, Mac files may be `forked': as well as the normal `data fork', they may have a `resource fork' which holds structured data such as custom icons, previews, etc.&nbsp; You'll probably only get the data fork of any files you transfer to your PC; but again, cross-platform file formats don't use resource forks, so that shouldn't matter to you.
</ul>Things like this are why the Mac has its own archive formats like StuffIt (.sit) and BinHex (.hqx); unless you do something clever, type/creator codes and resource forks would be lost if you put them in a .zip file.
<p>
(* There are exceptions.&nbsp; For example, Java applications packaged in .jar files will run on both PCs and Macs, as will scripted languages such as Perl.)
<p>
Simplest thing, as I said, is to try it and see