In Windows XP you occasionally need the install files to add additional features or to run a Windows repair. Instead of having to find the CD you can copy the install (cab) files to your computer.
Create a 2 folders in your c:\windows\ directory called options\cabs\
Copy the install files to your computer
Open a command prompt and type the following command to create the directory
c:\> mkdir c:\windows\options\cabs\
On the Windows installation disk copy all the files inside the i386 folder to your c:\windows\options\cabs\ folder

Tell Windows where the install files are located
Edit the following keys in your registry.

\HKEY_LOCAL_MACHINE\SOFTWARE\MICROSOFT\WINDOWS\CURRENTVERSION\SETUP\

Open the following key

Source Path

Change the Value data to:

c:\windows\options\cabs\
Now Windows will automatically find the install files.