I can guarantee that all the Oolite for Windows versions found on Berlios are virus free. Before each release, the game installer, as well as the installation image (i.e. the game tree installed on a user's hard disk), are thoroughly checked for malware using professional up-to-date virus scanning software, with latest at time of release virus definition files. Where did you download Oolite from? I have seen it appearing on various "free software here" sites, but only the copies downloaded from Berlios (or from www.oolite.org
, which poiints to Berlios for downloads) are guaranteed to be clear.
I would recommend uninstalling Oolite, running a full system scan after booting from a Windows start up CD or other means of booting clean and, once you are sure that all is in order, re-install Oolite.