Chaps, to shed a little light, turning Norton off worked, but could be co-incidental I suppose, since I also turned the machine off & reseated everything as an obvious first step.
In light of other comments on this, I know the hard disk on this machine to be corrupt in the sense that it has unreadable sectors & chkdisk runs but fails on every startup. That I suspect is the root of my probs.
I lost outlook express yesterday afternoon on the "msoe.dll failed to initialize" error, after the registry failed to load on startup, but booted itself from a log backup. Fixed that with a system restore, but ultimately, I have an unstable pc that probably requires a new HDD.
Thanks for your help everyone.