Exactly. Once you get a legal copy of the OS, M$ will give you all the updates and service packs for nothing for as long as they officially support the OS.
Tom
I remember when I first did this, xp pro sp2 hadn't gotten to stores yet and I upgraded from 98 to xp pro sp1. Everything was fine then, but when I downloaded sp2....
....nightmares of ME started flashing before my eyes. I backed up everything I needed in safe mode and formatted/reinstall sp1. It was another year before I tried downloading sp2 again.
I downloaded the SP2 executable and saved it to disc. I then did a clean install of XP SP1 from my OEM disc, put in my chipset drivers, and before installing ANYthing else, run the SP2 executable. Zero problems.
Tom