how to set up an intranet?

i am using windows xp.
can u hlp me now?
what are software that i need to instal

Do you mean you want to create an intranet for your office? If I undersand you, then you need to install a server, such as IIS. See Learn IIS7 and Install IIS 7 on Windows Vista and Windows 7. You can install IIS using Vista or Windows 7. There are server versions of Windows, and they are called server because they are made for IIS.
 
There are many other serevers you can use, such as Apache. See Comparison of web server software for a long list of others.

can you explain some details,please?