Naomi, the good news is that if it's Virtumondo then it's adware, usually loaded along with some other app.

The bad news is that if this sort of ancient adware has got through without alert, then other far more malicious stuff may have done the same. There are also other Trojans possibly using the same extension including some keyboard loggers. The big risk is that a keylogging hacker may have your online banking passwords or similar. Depending what you find on your PC, a rapid password altering exercise may be in order.

After that: consider Zonealarm. I've used it for 5 years and have yet to feel disappointed. It offers virus checking, spyware blocking but also a firewall that warns you if programs unexpectedly get changed or try to connect to the internet or attempt to send e-mails or attempt illicit writes directly to memory or whatever. That's useful, because when new malware appears there's always a window before its signature gets identified and added to the scanner, during which time the malware won't be detected. The firewall means that even if stuff does get sneaked in, at least it can't phone home. ;-) Also, if you haven't already you should implement MS's recommended outlook autopreview changes to prevent display of images, activeX controls or anything else except text unless you decide you want to look at it. That allows you to dump obvious spam before it gets a chance to sneak a payload onto your machine. Unless you're browsing shady sites or installing stuff you receive or download from unknown providers, email is the most accessible entry point- unless you're leaving your ports or netbios wide open. It might be worth visiting www.grc.com and running the "shields up" facility. If it gives you a shock, it's easy to install a cheap nat router that blocks netbios and most port access to your machine/s. Not perfect, but at least hackers get to hammer at the router rather than at your PC.

Hope you can sort it out. If there's any doubt, change those passwords!