build crash free network??

Setup the network and never allow any of the end users to install any software or apply Patches for either OS or Software.

I know it sounds flippant but really it is the only way and even then you need to take the system down on a regular basis when Patches are pushed out after testing from the server.

How big do you want to make this? If it is just a few machines it is different to several big Domains that control their own sub Domains.

Col

Is that crash free from software bugs or hardware failures as well.

If hardware then you need to spend a lot of money for fault tolerance equipment, and even then it will not be perfect.

Even the insurance companies and banks have down-time and they spend millions. :)

As Hal said ..The tighter the security the better the chances of survival..this includes restricting internet access and downloads and keeping away the possibility of virus, hackers and spyware.

Well if there is one let us know but a few steps to make it less painful. One is get the most current virus definitions and keep others from downloading patches that are not tested. Test the applications on a seperate test computer that is not connected to a server when running the test. get best firewall and router possible. and check for alerts and patches and limit users from touching server or any thing that you do not want messed with with permissions. We always test things throughly before letting people use the software to find the problems and train the people on correct proceedures.