Thanks for your reply.

It's still the same with Internet Explorer (no add ons), the only difference is, I don't get the error message when I close it.

I had a look at the system restore to see what had been done in the last few days. It seems to have happened since some Windows updates came through on Weds. I have restored back to before this time and it's ok now and working.

Update:- I installed the updates again and IE wouldn't work again. So I restored it back to before I did it and it works. I have checked for updates now and the only one to install is Windows Genuine Advantage Validation Tool (KB892130)

I checked my update history and when I originally installed them on Weds, one of them failed which was Security Update for Windows XP (KB945553).

there was also one called Security Update for ActiveX Killbits for Windows XP (KB948881)

Does anyone know what this one is for?