i have dual boot
with grunb as boot loader and redhat 9 as foperating system
i have 3 questions
1)

before linux installation i have microsoft boatloader as default but after linux installation, grub emerge as the default loader. now what grub did with the microsoft bootloader ?

2)
due to some errors, my linux is lost
now i have a problem when ever i start the computer , computer goes to grub prompt
how can i get rid of this
in other words ii want to remove the grub loader and make microsoft boot loader as default
tel me the command

3)
some days ago i have dual boot as win98 and redhat
but after installed the winXP i lost grub how can i get back this as a default boot loader ?

1 - It over-wrote it

2 - you can't boot linux with the Windows boot loader, so unless you want to be rid of Linux permanently, you have to stick with Grub (or lilo)

3 - Windows always over-writes the MBR: It's anti-social. To get grub back, get your Linux rescue disk (or download Knoppix) & re-run grub from within Linux

dear look at the 2nd question

i have removed the linux but grub is creating problem . i want to finish the grub loader and make ms bootloader back

and i think in 3 question
some commands r available (i have listen from some where )that can come back the grub loader
tell me these commands or command

i think command look like this
grub ?????\

Yes, but #2 is contradicted by #3. . .

If you mean you get the command prompt at grub and want the menu back, just entering 'help' will list all the commands it understands. You can't get the graphical menu tho, as you wiped the config file that creates it when you lost Linux.