YOu need to use Visual Studio .NET and check some whitepapers at
msdn.microsoft.com/sharepoint.

I've view the
msdn.microsoft.com/.../sha\
repoint_webparttemplates.asp
web but i can't found this pakage:
"Download the package containing web  Part templates for Visual Studio .NET
by clicking on the download link"
I can't know how start to develop  a new webpart  From Visual Studio .NET
Any idea?

From the SDK:
“Templates are stored either entirely in expanded format on the front-end
Web server as site templates, or as a combination of both expanded format on
the front-end web  server and compressed format within the database as custom
templates. When Microsoft SharePoint Portal Server "v2.0" Beta 2 is
installed on a server, site templates are created within the following
directory:
Local_Drive:\Program Files\Common Files\Microsoft Shared\Web Server
Extensions\60\TEMPLATE”
Also look through the SDK for guidelines on how to develop  web parts.

I can't found the SDK that u indicated en i email.
I vew that is so diferent, the method to develop  new WebParts like in V1
version.
I vew the \TEMPLATE folder , but i don't know that i do with this?
I can open a project in Visuatl Studio .NET to develop WebPart?¿

I'm currently develop in V1 and i need to migrate to V2, I've a lot of
Personalized WebPart to V2.

Try
msdn.microsoft.com/.../html
/sharepoint_webparttemplates.asp as a starting point.

Look around the pages at this point in the sdk.

In MSDN library traverse the following:

Web Development
...Server Technologies
……SharePoint Products and Technologies
………SDK Documentation
…………Microsoft SharePoint Products and Technologies v2.0 Beta 2 SDK Platform
…………….Windows SharePoint Services
……………….Concepts and Architecture
………………….Introduction to Templates

sorry but i can't found this tree in
http://msdn.microsoft.com/library/default.asp
My menu is

Web Development
Server Technologies
SharePoint Products and Technologies
SDK Documentation
Microsoft SharePoint Products and Technologies v2.0
Beta 2 SDK
Welcome
SharePoint Products and Technologies Overview
Plataform
Applications
Apendix
Glosary

Can u send me URL to view SDK?

If you haven’t already, have a look in the ‘Platform’ item. You will find
it there.

i read this from SDK:

"To create a new Web Part Library project
Start Visual Studio .NET.
On the File menu, point to New, and then click Project.
In the New Project dialog box, click Visual C# Projects, and then select
the Web Part Library template.
Note  If you want to create a Visual Basic .NET project, select the Web
Part Library template from Visual Basic Projects instead.

Type "SimpleWebPart" as the name and specify the location for the project
files, and then click OK."

When i create a new project from Visutal Studio .NET , I can't found "Web
Part Library template."
I need install aditional software?

The templates that you need aren't released yet. Keep checking back on the
SharePoint MSDN site.