This is a little old but here's something (Sir) Bill Gates said, agree or disagree, he has a point.

"Windows is a more secure system than rival offerings based on Linux or UNIX, specifically because Windows has been under such strenuous attack for the past several years."

"As the most popular system by far, Windows is constantly attacked and has borne a brunt of attacks that's simply unknown on other platforms. As a result, Windows has emerged as the most secure platform", Gates said.

"A high-volume system like Windows that has been thoroughly tested will be by far the most secure," he noted. "To say a system is secure because no one is attacking it is very dangerous."