As alluded to in this thread and possibly others I missed, Virex is not Tiger friendly. A background process will chew up a lot of CPU. Either use the script that came with the package to remove Virex, or use Spotlight to find all "Virex" entries and remove them (which will, in some cases, require an admin password). Unless you do, the background process will keep spawning at boot time (as opposed to when you log in, so it won't be in your Login Items). You'll likely need to reboot, esp. if you remove everything manually.