Microsoft's Internet Explorer has many security problems that have been documented in thousands of places. I won't repeat all that here. However, one comment from Microsoft's director of product management for Windows shows the company's cavalier attitude.
Microsoft has fixed some of the Internet Explorer security problems by releasing Service Pack 2 for Windows XP. However, the company has also announced that it does not plan to release any such fixes for people who use Windows 98, ME, or 2000.
Gary Schare, Microsoft's director of product management for Windows, has one suggestion for those who cannot use the latest patches in Service Pack 2: buy a new personal computer.
Pardon me? I should buy a new computer because your company won't fix the problems that it created? By the same reasoning, one might solve the security problems created by a car's broken door lock by buying an entirely new automobile.
You can read more about this in a New York Times article written by Randall Stross. He also points out that Microsoft's director of product management for Windows doesn't use Internet Explorer himself, even though he expects you to do so.
You can read all of this at InfoShop.org