Many thanks for the replies. I ran the Malwarebytes which picked up the usual cookies, and what looks like a nasty:
c:/sccfg.sys
showing as a hidden file and identified as a rootkit. I have tried to remove it, but I guess the clue's in the 'hidden file' bit and it steadfastly refuses to budge. Grateful for any further advice.
Incidentally, log4rescue rang back this morning and I told them I'd fixed the problem with anti-malware. End of conversation. I suppose I should have asked where they got my details from, but I just wanted them off my back at that stage.
