1) Can anyone recommend a good place for checking what each trojan/virus etc does and the best methods for removal?
While I wouldn't use their anti-virus products (bloatware) Symantec has great info on their site - http://www.symantec.com/security_response/landing/threats.jsp
2) Is there anything other than Avira I should be running? Though I can download programmes on the Mac and transfer them over to the PC for installation, it obviously can't be anything that requires web access to run (like McAfee did... duh!), obviously.
You could try McAfee's Stinger executable to do another scan using a different engine. It might find a few bits that Avira doesn't.
If you do get back online it might be an idea to use Spybot Search and Destroy - http://www.safer-networking.org/en/index.html. It can immunise your browser against many Internet based malware threats.
Also, I wouldn't pay for antivirus for home use nowadays. Microsoft bought security company Sybari years ago and released their own antivirus free for home users. http://windows.microsoft.com/en-GB/windows/products/security-essentials
I've been using it for quite a while now and it seems quite good.
Edited by Stratt (04/05/12 01:09 PM)