(posted: August 17th, 8:00pm) Computer users all over the world are trying to free their desktops and laptops from the grip of a virus that is circulating on the internet.

The "Zotob" worm brought some businesses to their knees on Tuesday, clogging up their networks and forcing some computers to reboot repeatedly. Experts say the problems really began last month when Microsoft announced a security flaw in its Windows 2000 operating system and hackers started looking for ways to exploit it.

Most companies have managed to get their systems stabilized, but one security firm warns it has already spotted four new versions of the worm.