What version of SharePoint are the web  parts meant for? WSSv2/SPS2003 cannot
use ASP.NET 2.0 web parts. SPS2003 cannot due ASP.NET 2.0 at all, while WSSv2
SP2 will support ASP.NET 2.0 for IIS, but not ASP.NET 2.0 web parts.

If you want to develop for WSSv3/MOSS2007 (currently in beta) you can use
these tools, but there is very little in the way of developer environment
documentation so far. Look for an MSDN whitepaper in a few weeks through with
my company's name on it

The best general article on identifying web  part platforms and
development techniques that I have found is "Web Part Platforms and
Development Techniques,"
www.microsoft.com/.../webpar
tplatforms.mspx. The "Visual Web Developer" referred to in this article
is installed by default in Visual Studio 2005.

A good walkthrough to start with is "Walkthrough: Creating a Basic Web
Page in Visual Web Developer," at least to the point of creating a web
site. Then the introduction to web parts  video by Thom Robbins,
perseus.franklins.net/.../webparts.html will show
how to set up an actual web part.

The walkthrough on creating a website uses the VS2005 built-in "ASP.NET
Development Server", not IIS. Information on how to use this web server
in VS2005 can be found in the article "Web Servers in Visual Web
Developer," msdn2.microsoft.com/en-us/library/58wxa9w5.aspx.

I think that when the website is created as an "ASP.NET Web Site" as
described in the walkthrough that SQL Server 2005 Express Edition (the
SQL Server installed by default with VS2005) is set up so that web parts
can run in VS2005

This little experiment appeared to produce a working Web Part without
the necessity of installing/configuring IIS. Setting a reference to the
"Microsoft.Sharepoint.dll" file appears to be unnecessary. I have tried
the project/solution with and without the file and it seems to make no
difference. However, as can be seen from the attached screen shot, the
down arrow icon that allows selection of "Minimize" or "Close" from a
pull down menu is not present.

Nonetheless, I think these three sites would allow someone to develop a
simple web part and see how that works on Windows XP with just VS2005.
However, more complex web parts might or might not be doable and getting
the web part in a state to deploy also might not be doable.