I know the normal way;

You can install IIS using the following steps:

1. Click Start and select Control Panel.
2. Double click the Add or Remove Programs applet.
3. Select Add/Remove Windows Components.
4. Place a check beside Internet Information Services (IIS).
5. Click Next.
6. If prompted, insert your Windows XP CD.

HOWEVER, on this particular stripped build of Windows XP I'm working with, Internet Information Services (IIS) dosen't even show under 'Add or Remove Programs applet'. Is there a way I can manually install it from the WinXP Pro CD?