Why can't I reinstall Windows with SP1 on it after installing SP2?

I went to do a reformat reinstall of a OEM version of windows XP that had SP1 one on it and I got a message saying I cannot install XP becuase it was a previous version of windows. Has anyone heard of this? If so what is the work around?
I ended up loading a pre SP2 image from Norton Ghost then was able to do the reintall and of XP. Seems like a lot of work everytime I want to reformat and load a fresh version of windows. I am hesitant to download SP2 again if I have to go through that everytime.

you shouldn't have to do that at all, ever, if you load the OS by booting from the CD and starting your install that way.

Boot from a 98boot disk and run FDISK /MBR and that should clear up your problem.

I forgot to have the system to boot from a CD first time. So it sounds like having SP2 shouldnt effect the reinstall. Good

SP2 wont affect an instal if you boot from cd - if you try installing from windows yes you get that error.