Not sure about the website posted. But I believe it may provide torrents to all kinds of files. Some of which may be legitimate and some which may not.
As for the operating system.
There are many reasons why one would want to use a Server OS as a Workstation OS. See
http://win2k3.msfn.org/ (Server 2003) and
http://www.win2008workstation.com/ (Server 2008).
Windows Server 2008 was known as Windows Server Codename Longhorn (which is similar to what Vista was called during most of it's development before release). Server 08 has basically the same inner core as Vista. So think as if you're running a stripped down, optimized, server-oriented version of Vista.
This takes us to your specs - Microsoft lists the minimum/recommended sys requirements on their site:
http://msdn.microsoft.com/en-us/wind.../cc196364.aspx
If you're looking for a lightweight Windows OS for a PIII with 256, I would suggest looking into Server 2003. If you have some time on your hands.. linux is always a fun experimental alternative to windows users (I hope
.