Ques. 1
It is recommended that we first install windows OS then install Linux and then use LILO or GRUB in case of dual boot (Windows 2000 & Red Hat Linux) as Installing windows later will overwrite MBR.
Suppose I have installed both the OS and in future Windows crashes, then how to reinstall Windows without affecting linux. Is there any way or do I have to install both the OS afresh.

Ques. 2
Also I do not want to use LILO or GRUB at boot prompt(i.e. when I start computer, it should start windows only and nobody should know whether Linux is installed. So which way to install Linux to acheive this.

Dude - if Windows crashes, the corrective action is just to reboot. You won't need to reinstall anything, unless you are defining a crash as a complete failure/corruption of the OS. If that's the case, you won't have any choice except to reinstall.

As for hiding Linux at bootup, you could always set the wait time to 0 seconds, but of course that would prevent anybody from ever booting up Linux.

My question to you: Why go through the trouble of setting up a dual boot Win/Linux system if you only want people to use Windows? -- J.W.

If you're not planning to use LILO/GRUB, then the first question is solved cus you don't have to worry about windows killing grub/lilo when you reinstall.
Although I don't see any reason why you want to do this but my suggestion is that install redhat without any bootloaders, then create a bootdisk, boot with it whenever you want to boot linux.

Thank you Mr. J.W. & Demonbane for your reply.
Actually My computer is used by my friends in my absense who do not know about Linux. I just don't want them to get confuset at startup.I think better to tell them what to select.

Also, It is not clear whether to reinstall only windows or both (linux & windows) after windows crashes(unrecoverable crash).
Or
Start linux from floppy, copy boot sector then reinstall Windows and copy boot sector file in c:\ and add to boot.ini.