Unfortunately, this will be a regular feature on this site, as new and potentially dangerous virus/worms emerge. The latest is Sasser
Once infected, Sasser will reboot your computer ever few minutes. Although it can only infect Windows 2000/XP systems, older Windows systems can still help to spread the worm to other vulnerable systems, and waste the system's resources and prevent programs from running.
Windows Update already has a patch which fixed this vulnerability, but a removal tool from Symantec is also available
for systems already infected.
For free anti-virus/firewall software download links and tips on how to avoid infection, please head on to this forum thread