So I've got Windows XP Pro on a CD. This is the original Windows XP CD no SP1 or SP2. Now, If I want to install Windows XP, I have to go install Windows XP, then two service packs. This can take forever. Microsoft releases all new XP media with the service packs integrated.
What this process does, is takes your original CD and adds SP2 to it.
This process does not use non-microsoft files, so you don't need to worry about it being tainted by spyware, viruses or malware.
You can check out how you make a XP CD into a SP2 CD here.