The information applies to when using the ISO image to upgrade to 2003 with SP2a is in progress and the installer generates the error “Please insert the disk: 1”.

The error shown in the screen capture will occur when the installer starts to copy the new files in an attempt to upgrade a previous version of 2003 to 2003 with SP2a. To work around this issue, see the solution below.
1.  Click “Cancel” to abort the upgrade
2.  Explore the ISO image and locate the folder which contains the install files for 2003 with Sp2a (see image below)
3.  Select the sub folder “ 2003” and copy the folder to the local hard drive, e.g. Desktop
4.  Open up the folder ( 2003) and locate the executable file “ 2003 Setup.exe”
5.  Double click the executable to restart the upgrade using the local copy of the install files
6.  The upgrade will complete successfully