How can I create a full webpart , that i can import in SharePoint 2007.
What do you require this web part to do?
You can create Data View Web Parts in SharePoint Designer 2007, which you can "Export" via the Web Interface. This produces a .webpart file which you can upload into the Site Web Part Gallery.
If you require more complex functionality you will need to produce a .NET assembly which will need to be deployed by a server administrator.
Whichever method you choose is dependant on the business requirement for your web part.