1. Download:  Download the path from Microsoft HERE
2. Copy: Copy the ENTIRE contents of your windows CD to a working directory.  Your windows CD must have SP2 already. For this example we will make believe my CD is in my “E” drive and I am working out of a folder called “c:SP3_cd”  I would copy everything from the E drive to c:sp3_cd, this can be done with drag and drop or by using xcopy:
   xcopy /e /r /y  e:*.* c:sp3_cd




3. Integrate:  From command prompt CD to the location of your downloaded SP3 file and run the integrate command.  For my example I will use:
    WINDOWSXP-KB936929-SP3-X86-ENU.exe /integrate:c:sp3_cd
4. Rip: Using a utility called bbie (click HERE) rip the boot sector off your windows CD.  Again from command line navigate to the location of your bbie and simply input the source CD.  To drop a file called “image1.bin” in the same directory as your bbie.exe I would run:
   bbie.exe e:
5. Make: Make a ISO with your folder and boot file.  Use Nero, or Magic iso to burn the contents of your patched CD.  Be sure to use the boot file we created.  Select bootable form them menu.  Alternitivly you can download barpe builder HERE. This package contains a file called mkisofs.exe from command line we can pass it a ton of arguments to make it output a iso. Change the colors to match your paths.
   
   mkisofs.exe -force-uppercase -iso-level 4 -A mkisofs -sysid “dos” -b c:image1.bin -no-emul-boot -boot-load-size 4 -hide “boot.catalog” -o c:SP3.iso c:sp3_cd
6. Rejoice:  If you are like me and install windows a lot this will save you lots of time.  

Note: mkisofs is insanely complex switches.  If you have nero or a application with a GUI to browse to the source, boot image and output it makes it much easier.