I popped over and it looked to be virus ridden. XP Home system, couldn't load anything, kept being told the program was infected and the system wouldn't allow it to be run. In the end I brought it back and rebuilt it from the recovery partition. All OK.
Two weeks ago I got a call saying it had 'gone again'. Popped over and had a look. The wallpaper had been changed to various bits of text about being infected with viruses, malware, etc.Couldn't run applications, e.g. MalwareBytes, being told the file was infected. Messages appear to be coming from something, I think, was called, Tool Kit. As I hadn't the time then to sort it I suggested he switch off and leave it and I'll get back to him.
I rang him this afternoon to arrange to sort it out. He told me that he'd left it for a week or so then last week decided to switch it on. Lo and behold it was working just fine, no strange wallpaper, no strange messages, email working fine.
It appears to have fixed itself. He did ask me if I had sorted it 'from my end', clearly I hadn't.
I've no idea what was wrong with it two weeks ago then given that a week or so later it 'fixed itself'