Ok, I stuffed up.
I have uninstalled something and no I have no sound.
Windows detects a PCI device when booting though it can not find a driver for it.
I have run through all the cds that came with my Dell laptop and tried to install what I could with no luck.
The Sigmatel installation stops saying "no supported device"
The only way to get sound is to boot of the diagnostic CD and run a sound check.
System:
Dell XPS M1710
Windows XP SP2