Alan Zisman -> All said..

 AZ> I tried going the Esset online scanner -
 AZ> http://www.eset.com/online-scanner - it failed to download its
 AZ> malware definition file (repeatedly) and so wasn't able to
 AZ> run.

Boot into "SafeMode with networking".

Open the browser and download Malwarebytes: http://www.malwarebytes.org/ 
..and install, and run it to scan for nasties.

The key is the boot in SafeMode with networking.  The on-line scanner may
cooperate better too.

--- Thunderbird 2.0.0.24 (Windows/20100228)