erasing a harddrive

is it possible to write-protect a hard drive?

i have tried fdisk, and debug to clear out a hard drive in a laptop and nothing will write to the hard drive. whenever I reboot the laptop, I get a message: save disk disabled.

the hard disk I am trying to format has linux installed, I want to delete linux and install windows, but as I said above, it won’t let me. and I don’t know anything about linux, no commands, troubleshooting, nothing. I just want to uninstall linux, and install dos/windows on the harddrive, but for some reason i can’t.

any suggestions?

thanks.

-estela