I have been having a few issues installing software on my (old) Sony A197XP VAIO, notably Firefox 3 and iTunes 7.7 (which I wanted to install for MobileMe).
So before I re-install Windows (and all the headaches that will cause me) I decided to try and install XP SP3.
This did install.
I was then able to install Firefox 3.01 and was pleased with that.
However iTunes 7.7 still failed to install.
Not sure where to go now, but looks like I may need to reinstall Windows.
http://support.apple.com/kb/TS1496
Mentions problems with iTunes after SP3… not sure if it directly applies…