Installing Windows SharePoint Services 3.0 for the first time

1. Install Windows 2003 Server, member of a Domain

2. Install IIS 6.0 (If Upgraded from IIS5.0 Run WWW service in IIS 5.0 isolation mode check box must be unchecked)

3. Download Microsoft .NET Framework 3.0 Redistributable Package
http://www.microsoft.com/downloads/details.aspx?familyid=10CC340B-F857-4A14-83F5-25634C3BF043&displaylang=en

OR

Download Microsoft .NET Framework 3.0 Service Pack 1
http://www.microsoft.com/downloads/details.aspx?familyid=EC2CA85D-B255-4425-9E65-1E88A0BDB72A&displaylang=en

4. Install Microsoft .NET Framework version 3.0

5. Enable ASP.NET 2.0
In the IIS Manager tree, click the plus sign (+) next to the server name, and then click the Web Service Extensions folder.In the details pane, click ASP.NET v2.0.50727, and then click Allow.

6. Download Windows SharePoint Services 3.0http://technet.microsoft.com/hi-in/windowsserver/sharepoint/bb400747(en-us).aspx

OR
Download Windows SharePoint Services 3.0 with Service Pack 1 (SP1) [Must for Windows 2008 Server]http://www.microsoft.com/downloads/details.aspx?FamilyID=ef93e453-75f1-45df-8c6f-4565e8549c2a&displaylang=en

(Note - For Simplicity we are doing SINGLESERVER Installation which means we are using SQL Desktop engine & do not need SQL Server Full version)

7. Run Setup
1. On the Read the Microsoft Software License Terms page, review the terms, select the I accept the terms of this agreement check box, and then click Continue.
2. On the Choose the installation you want page, click Basic to install to the default location. To install to a different location, click Advanced, and then on the Data Location tab, specify the location you want to install to and finish the installation.
3. When Setup finishes, a dialog box prompts you to complete the configuration of your server. Be sure that the Run the SharePoint Products and Technologies Configuration Wizard now check box is selected.
4. Click Close to start the configuration wizard.

8.Run the SharePoint Products and Technologies Configuration Wizard
A. On the Welcome to SharePoint Products and Technologies page, click Next.
B. In the dialog box that notifies you that some services might need to be restarted or reset during configuration, click Yes.
C. On the Configuration Successful page, click Finish. Your new SharePoint site opens :-)

For Details & Advanced Installation Options Please Refer:
Installation Guide for Windows SharePoint Services 3.0http://go.microsoft.com/fwlink/?LinkID=107358