Xolox have withdrawn their product, but it is easy to get it going again. If you operate behind a firewall then simply block the site http://www.xolox.nl. End of problem.
If you don't have a firewall, there are ways of doing the same thing. however I suggest you do get a firewall, as using these file-sharing utilities does advertise your IP address and this potentially attracts hackers. A good (free) firewall is ZoneAlarm.