|There are a number of anti-virus scanning products you can download and load onto a CD or flash drive. It is as simple as putting the device into the server and running it. Sometimes viruses can compromise your antivirus you have installed.|
McAfee, Norton, Symantec and AVG will all have their own versions of this product.
Also, Panda has a download that you install to a disk and you set your system to boot to it. Doing it this way will prevent your system from loading the virus as your try to scan for it. The downside is it will take your website offline.
Is your Web site hosted by another company? if so, they may be able to provide a service to help remove it.