Damn, I can't remember the name of it - I'm typing this at home, and the thing was on my work computer. AVG picked it up as a warning, but didn't pull the thing itself. Basically, it hijacked IE and Firefox, giving me a Cod Microsoft Page towards 'AntiSpyware.com' and put up a recurrent little VB Box with the message Hehehehehehe! which popped up over everything every ten seconds.
I ran AVG 8 - then Downloaded MalwareBytes - ran both of them - NOTHING! So I googled the details, and found a forum which had tales of a similar infestation - followed someone's advice on which registry keys to eradicate, uninstalled WinRar - turned off system restore, rebooted, ran Trend's HouseCall - turned system restore back on - and it seemed to have gone - BUT - for the rest of the day, Google kept warning me that something was attempting to hijack the browser, so I think there may be a trace left. Housecall, weirdly finished in about fifteen seconds, so I'm not sure what was going on there - I will run everything again on monday when I get in to work, and see what occurs - Wise Disc and Registry Cleaner, Windows Defender, and all the others. I'll also trawl the registry and get rid of any WinRar evidence. ZipGenius was recommended to me, so I will eradicate WinRar forever