What is the most reliable operating system?

Windows operating system is always reliable and best if used with the respective hardware requirements and if upgraded a little higher than that. As such, Windows is reliable and best in operation as mentioned by most of the people, but in most cases this reliability is affected mostly by hardware components and some software components - hard disk failure, RAM failure, overheat, security breach, etc. If these issues are solved with suitable tools, any version of Windows is reliable.

I would agree with Windows 7, my current system has been running for 3 years used every day and has been extremely stable.

I should say it does depend a little on the software. I don't run suspicious software and if I want a utility to fix a particular problem I will install it, run it then uninstall to leave my system as clean as possible.

They were all the best in their day.. well maybe not ME. Windows Millennium was the only OS which could crash without any user intervention. Having said that, if it was run on a Windows 2000 spec machine, it was OK..

XP didn't come good until the SP2 update in 2004, but it was way better than its Windows 9.x cousins. Looking back, it was fast and furious, but a little sloppy compared to what followed.

Vista was great on a machine with enough power to run it, and it forms the base of Windows 7 and 8. Vista's strength was that it checked and double checked everything that it did. It's weakness was that it took forever to do it, hence the need for top flight hardware..

Windows 7, the last of the 'desktop only' operating systems is probably the best to date, but then again, it has had longer to prove itself than Windows 8.

Windows 8 makes for a really good desktop OS, but I think that the Modern UI needs work doing on the apps and general app reliability. It is still early days.

All of the recent Windows operating systems can be pretty reliable. The problems tend to arise with particular drivers and software and how he computer is used.

If you are planning to go for a new computer then I would go for Windows 7 or 8 to give you more future proofing.

Peoples will give differing answers based on their experiences. Personally I have had minor issues with Winxp and none with Vista, Win7 & Win8 on systems that run 24/7, current win7 systems have run this way for 3 years