I know this does not work impromptu. Is there a way of installing a free AV scanner?
I would prefer Microsoft Essentials or Antivir.
You would install it just like any other Antivirus scanner, however, a lot of products such as Microsoft Security Eseentials are not designed for Server 2008 and will not install on it.
Just check operating system compatibility before you download. I am not sure of many free AV products that support a server OS simply because they sell business/enterprise products and just give away a consumer product for free in order to get their brand known.
Over on Server Fault they’ve discused this issue a few times. Here is a link with several options for you. what-anti-virus-for-windows-server
Hope this helps some.
One of the few free AV scanners I know that will work in Windows server is Clam AV, however it does not do real time scanning, it only does scheduled scanning.