How do I disable GRUB from rewriting the MBR each time it is loaded?

Grub rewrite the MBR when it was installed not when it loaded.
Then what is your problem?

Grub only updates the MBR when installed to the MBR.
That is, you are telling it to.

To ensure it is written where you want (presumably a partition rather than the MBR), use the command line. Then you have total control.
See the grub documentation on the gnu.org site.

I had Windows 98, Windows XP installed.
Recently I installed Linspire which installed the GRUB boot-loader with it and rewrote th MBR.

But I wanted the Windows XP boot-loader as the default boot-loader so I restored the Windows boot-loader and added an entry to the boot.ini file to load the GRUB boot-loader, and this worked fine to enter into Linux.

But my problem is that, each time I load into the Linux, GRUB rewrites the MBR and sets itself as the default boot-loader.(And thus I have to restore the original MBR to set NTLDR as the default boot-loader)

So I want to disable the setting which is making GRUB rewrite the MBR each time I enter Linspire.

I'm not sure that this helps you, but it may get you looking in the right direction. As far as I know, there is no GRUB setting which will cause it to rewrite the MBR all the time. Typically GRUB will only rewrite the MBR if it is asked to. I would look for more information about a linspire setting and not so much for a grub setting.

I would agree with the other posters. Either GRUB is installed in the MBR or it is in another partition. Whatever boot loader comes up when you start the computer is what is installed in the MBR. If what you are describing is that GRUB comes up when you choose the Linspire entry from WinXP, this is normal operation. AFAIK you cannot boot Linux directly from WinXP, it must go through GRUB first.

Bill

I think it is Linspire 's problem, not grub.
To tell the truth, I don't know how can you use boot.ini to load linux.
But I suggest you using grub to load both linspire and XP.
I think it is easier

I agree - this is not normal grub or Linux behaviour.
Ask this question on the linspire.com support page - sounds like they "look after" you in the initscripts somewhere.

And using ntldr is a valid way of multi booting. The distro should not unilaterally take over this decision. Ask them, and allow them to explain.
Did you leave the "Install to MBR" box ticked during the install ???.