Windows PC owners are advised to trash any e-mail messages claiming to provide a fix for flaws in Service Packs 1 and 2.

The messages are actually from hackers trying to lure unsuspecting users into following the download link. Instead of fixing the ostensible flaw, the program on the other side installs malware onto the user's computer. Trend Micro, a security solutions provider, is sounding the alarm on this practice

Spam e-mail messages claiming to provide important updates for Windows users are unfortunately nothing new, says Microsoft spokesman Thomas Baumgaertner. He warns users to install only security updates delivered directly from Microsoft itself. The company releases security updates online every other Tuesday at update.microsoft.com, and in the event of an emergency.

"We never send software by mail," Baumgaertner says. That means that any email claiming to have an update as an attachment is a fake, no matter how persuasive it seems. "We would never do any more than send a link that leads to our site."

The safest bet is to set the computer to install the updates automatically, the Microsoft spokesman notes. To check if the function is already on the computer, open the "Windows Update" function in the control panel.