Here are the basic calls and the info that they extract from your PC:


Now to extract the actual browser from the browser info, insert this HTML on your page:
"<script LANGUAGE="JavaScript">
if (document.all)
var version=/MSIE \d+.\d+/

if (!document.all)
document.write("You are using "+navigator.appName+" "+navigator.userAgent)
else</script>"

And how to extract the OS:
using Notepad, generate a script file (maybe, getos.js) that contains this:
"function isJavaAvailable()
{
if(navigator.javaEnabled())
return ("is");
else
return ("is not");
}

function getOS()
{
//alert("" + navigator.appName);

if(navigator.appVersion.indexOf("16") != -1)
{
return("Win 3.1");
}
else if(navigator.appVersion.indexOf("95") != -1)
{
return("Windows 95");
}
else if(navigator.appVersion.indexOf("98") != -1)
{
return("Windows 98");
}
else if(navigator.appVersion.indexOf("SunOS") != -1)
{
return("Sun");
}
else if(navigator.appVersion.indexOf("Linux") != -1)
{
return("Linux");
}
else if(navigator.appVersion.indexOf("Mac") != -1)
{
return("Macintosh");
}
else if(navigator.appVersion.indexOf("Windows NT 5.0") != -1)
{
return("Windows 2000");
}
else if(navigator.appVersion.indexOf("Windows NT 5.1") != -1)
{
return("Windows XP");
}
else if(navigator.appVersion.indexOf("NT") != -1)
{
return("Windows NT");
}
else
{
return("Hmmmmmmmmmmmm?");
}
}"
ignoring - obviously - the first and last "  !!!!!!!!!!

Then on your page, insert this html:
"<script language="JavaScript" src="getos.js"></script> <script>
document.write("The Operating System you are using is <font color=red><b>" + getOS() + "</font></b><br>");
</script>"
and post getos.js to the same on-line directory as the HTML page, so that the page declares:

www.andytracy.net
and also see:
http://www.javascriptkit.com/javatutors/navigator.shtml
http://www.gurusnetwork.com/tutorials/javascript/javascript101/javascript101-6.html