Direct X 8 vs 9

Windows Xp sp1 on 1 computer. Xp sp2 on the other!
sp1 plays games fine! (Direct x 8) not so with sp2 (direct x 9)
Question... I dont want to down load a program or install aprogram that will upgrade my sp1 computer to direct x 9 . It happened once , there dosent seem to be any warning, nor did it (program) ask.
I installed a web camera, which was great! howerver i discovered later I now had direct x 9 and games wont play!
So is there a way to prevent this from happening ?

 

weird! I dont think its because of directx 9