Which OS is more secure Mac OS, Windows, Linux?

It would definitely be linux although I am currently using Windows since linux don't play Window games and not yet fully plug and play.

Linux is Better one ,if u go for GUI XP has more compatibility for any applicaton & any hardware rather than other

I am a Windows user; actually, I am a Microsoft user. I have been using PCs since DOS 5. The reason Windows commands the market is because it does more than any other operating system. Also, since PCs can be upgraded piece by piece, they are cheaper in the long run. Mac users always try to say that Windows is unstable and vulnerable. The real reasons for this are: A) You are limited in software, and particularly in hardware (everything is inbuilt). Few components can ever be upgraded, and it's usually only through Apple. B) Hackers and malware authors/distributors focus on the operating system that everyone uses, because they get the most hits that way. I am a tech, and I treat my machines the same way you'd expect a dentist to treat his/her own teeth. I use a conservative registry cleaner to take care of orphaned entries, I use WinDoctor to clear up program errors and locate missing DLLs, I clean temp files regularly, and I defragment monthly. If I ever make changes, I backup my OS first. I back up the registry, then create a restore point; if I'm about to make a major change, I backup the whole drive in Acronis. Between the above-mentioned measures, as well as using the right security software (particularly my NIP firewall); my machines run consistently fast, stable, and secure. My favorite joke, valid or not, is that Macs are for the PC-illiterate.

I am a mac user since 2001 and I never had problems...

Windows Vista is more secure it has good security & encryption options 7 it changes sys files randomnly for every boot upto windows xp the boot information stores in Boot.in file and now vista come up with BCD