Windows XP boot issue

[factorPlayer]

So I finally broke down and installed service pack 2 after holding out a couple years.

But now everytime the computer turns on it tries to load Windows Setup and fails because it can't find the iastor.sys file, and it has to reboot.
Then I can choose to have it load Windows XP instead of Windows XP Setup and everything is dandy til the next time it has to restart.

Just annoying having to do baby-sit it that way everytime I want to turn on the PC.  Anyone know how to force it to just load the OS instead of the Setup?

[OverCaffeinated]

If it is a desktop always leave it on. If not I can't help.

[derby]

open up c:\boot.ini in notepad. it'll look something like this:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /NoExecute=OptIn

make sure your default= line points to the same arc path as your "microsoft windows xp professional"

edit:  (or you can cheat and do it through msconfig as detailed here: http://vlaurie.com/computers2/Articles/bootini.htm)