Okay, I'm about to give ComboFix a try - had to download it on this laptop, though, because the links all came up error 404 on an infected machine...

The Malwarebytes files could be useful - mudcat_at_bernardcromarty.co.uk - thanks, Nick.

John - I'll have a go at the downloadable updates if the above two fail to find anything, thanks. It's possible everything I need will already be in the WSUS folder on the server at work, with any luck.

Off to try ComboFix now...