Can I install a custom Web Part on my SharePoint Services 3.0 site
From mail2web.com Wiki
To add a Web Part to your collection, you can follow these steps:
1. Log on to your SharePointâ„¢ Services site. From the Site Actions menu select Site Settings 2. Under Galleries click on Go to Site Administration 3. Under Site Collection Galleries click on Web Parts 4. From the Upload menu select Upload Document or Upload Multiple Documents 5. You can then Browse to the location on your computer where the .dwp or .xml file is located and upload to the server.
Please note that we do not support the installation of Web Parts which include additional support files or have custom security requirements.
