you can use a scanner like clamAV portable that doesn't need installation
and does not have a resident shield and is free

http://portableapps.com/apps/utilities/clamwin_portable

"Neil Jones" <castellan2004-nschap@remove-this.yahoo.com> wrote in message
news:OPSVk.1379$ve.262@newsfe23.iad...
> What is the best way to use 2 or more virus scanners on the same system?
> I want one of AV scaaners to be the primary AV scanner (resident). The
> other AV scanners I would like to use them from a bootable CD or as an
> application and execute on-demand only. Some scanners seem to be more
> current than others. So I would like to know if anyone has done this on
> Windows Vista without hurting the system.
>
> Thank you in advance.
>
> NJ