If you are struggling to integrate the Silverlight and MOSS
Here is the solution for your problem 
1. Part 1 (Silverlight project DLL to be copied into this ClientBin Directory)
1. Create ClientBin Directory under this folder (C:\Inetpub\wwwroot\wss\VirtualDirectories\80) Default web app
2. Open IIS Manager and locate the ClientBin Directory Created in step 1
3. Choose the property window of CilentBin
4. Change the Execute Permissions: to Scripts Only
2. Part 2
1. Create a Project in Expression Blend
2. Build and Test the project.
3. Copy the DLL ( created under ClientBin directory of the Silverlight project) into the Sharepoint application ClientBin Directory (C:\Inetpub\wwwroot\wss\VirtualDirectories\80)
3. Part 3
1. Upload the XAML file to sharepoint application
1. SiteAction ->View All Site content
· Option 1
Create -> Documentment Library
Type SilverlightPages ( anyname ) into Name Textbox and click create button
Upload the XAML file into the Silverlightpages folder
· Option 2
Click on pages
Upload the XAML file into the Pages folder
2. Publish and Approve the file ( if needed )
Add the following code into your sharepoint page or custom master page
Option 1
<div id="SilverLightTopPanel"> // you can specify id
<script type="text/javascript">
Sys.Silverlight.createObjectEx({
source: "MasterPageTop.xaml", // Specify your xaml file
parentElement: document.getElementById("SilverLightTopPanel"), // specify your Div element ID
id: "SilverlightControl",
properties: {
width: "1024",
height: "60",
version: "0.95",
enableHtmlAccess: true
},
events: {}
});
</script>
</div>
Option 2
<div id="SilverLightTopPanel"> // you can specify id
<script type="text/javascript">
createsilverlightmenu()
</script>
</div>
You can create function as a seprate (JS) file and upload into proper location
For example createsilverlghtobjects.js
function createsilverlightmenu()
{
Sys.Silverlight.createObjectEx({
source: "MasterPageTop.xaml", // Specify your xaml file
parentElement: document.getElementById("SilverLightTopPanel"), // specify your Div element ID
id: "SilverlightControl",
properties: {
width: "1024",
height: "60",
version: "0.95",
enableHtmlAccess: true
},
events: {}
});
}
Copy this (createsilverlghtobjects .js) file into C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS\1033 (Sharepoint sever)
3. You have to copy the silverlight.js file (from Microsoft ) into C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS\1033 (Sharepoint sever)
4. You have to specify the file location into your master page ( Add the blow code into your custom master page ( inside head tag)
<SharePoint:ScriptLink ID="ScriptLink2" language="javascript" name="silverlight.js" runat="server"/>
<SharePoint:ScriptLink ID="ScriptLink3" language="javascript" name=" createsilverlghtobjects.js" runat="server"/> ( for Option 2 )