mchain
2
Fred S,
Welcome to the forums.
Avast! is a definition-based antivirus, as are all the other antivirus vendors currently available. All of them need to see a malware based code or executable to provide definitive protection against that specific malware.
If you should ever be unfortunate enough to encounter this rogue program again, you can submit the executable to this website here: http://www.virustotal.com/ where this can be examined by 43 antivirus scanners. I believe Virus Total is used as one of the central databases for suspicious files; most reputable vendors will check here for suspicious or malware files at least once a day.
A scan results page at Virus Total re an innocuous file, advisor.exe, made just now, shows the following results: http://www.virustotal.com/file-scan/report.html?id=2d6bd383131041208ca45302ce0c496e35d714760e6878f3e444eb8b541ab505-1322993188
Antimalware vendors such as Malwarebytes do a better job of removing rogue programs and similar as that is all they do; antivirus vendors must cover a greater myriad of malicious code to protect their consumers.
Malwarebytes is here: http://www.malwarebytes.org/ and is quite effective in what it does.
If you wish, you can consult the sticky posts at the top of this forum for more information on how to post infection logs, what programs to use, and so on. Programs such as OTL and ComboFix are best used only under the guidance of a resident expert here such as Oldman or essexboy. ;D