Active Unable to rid computer of ATDTM cookie.

[Active] Unable to rid computer of ATDTM cookie.

I have a fairly new Dell, Inspiron 1525 laptop.
Each time I open Windows Live Mail, the annoying ATDTM window pops up.
The computer is kept clean with all the usual cookie/malware/virus removers. I have tried removing this ATDTM manually with no luck.
Searching the web, I see that many others have the same problem with this thing coming up when using Windows Live Mail. I have followed instructions from others but it still returns.
Contacted msn but they were of no help.
Does anyone know how to really get rid of this miserable tracking cookie please. It's incredibly annoying.
If nothing works, should I/can I, uninstall/reinstall Windows Live Mail without messing up anything else in the computer? I don't use it for email usually, but my husband does and he says it shouldn't be uninstalled.
Any help would be greatly appreciated.
Thanks
LizzieD