Thank you everyone so far.
The Boot up scan suggested by F4 (Thank you) identified a lot of files infected by Trojan-191 (and I think later variants). Unfortunately, getting rid of them seems to be a little difficult, most of them were in System and System32.
Consequently, I'm a little wary of deleting them and they won't repair.
Any thoughts on just deleting them all, as they're id' and downloading clean replacements as they crop up as errors?
I'm going to get these little beasties!
Maurice