Panda still offers a free online scane via active-x and IE7. The last time I checked Kaspersky (this week) , they were now offering a temporary download of their scanner. It requires uninstall of an existing scanner, but since you have none, that might fit your needs.
I still run Sygate PF on an XP and a Win98 PC. I've seen that message before and got worried too. My answer to being worried is a reformat, but I have spare drives with known good installs to copy. I'm sure you don't want to do that.
Try a System Restore. You might have to re-install sygate too. Some of the last versions of Sygate are available at oldversion.com.