First I don't know what you mean by 'I was trying to run the security tango' ?
You don't mention what type of scan you did or the amount of data on your HDD or your system specification, so it would be hard to say one way or another.
If you set it off on a Thorough scan with archives then it could well take a long time depending on the points I raised above.
avast has a boot-time scan, which you probably saw when you installed avast, that would be considerably quicker. If you have XP, vista32bit or Win2k, you could enable a boot time scan. Right click the avast icon, select Start avast! Antivirus, Menu, 'Schedule boot-time scan...' Or see
http://www.digitalred.com/avast-boot-time.php.
Or you can run an on-demand scan from safe mode but set the sensitivity to a Standard scan without archives.