fixboot fixmbr? winxp

I have a very ordinary Gateway laptop with XP Pro SP3 on it.

I am not sure if this is an os or hardware question but what I am trying to do is to fix the mbr/boot sector of an old Seagate 34gig drive which was internal and is now externally connected by way of a usb line. I can see the drive and files with no problem but I am banging my head against the wall trying to rewrite the boot sector.

When I try to boot off the drive it does try but dumps me into what looks like a prompt that says:
> grub rescue

I tried every command I could think of and the only one I could get to do anything was by using the Unix 'ls' command. That showed me what looked like a bunch of devices but that was all I could see. I have a recovery cd that came with the PC from Gateway that looks like it would work if I had a catastrophic failure and was willing to wipe my main disc clean but I cannot get to a dos command line where I could try typing something like:

fixmbr f:
fixboot f:

Where 'F:' is the extra hard drive I am trying to revive. I have done alot of searching and am starting to think that I need an bonafide MS Windows XP install cd to rewrite this mbr and get this drive back online.

Could that be true? I have also been looking high and low for some kind of 3rd party 'fixboot' or 'fixmbr' and am finding nothing except the directions for doing this with a Windows XP install disc. I do not have a Windows XP install disc.

Thanks very much,
Jim Lee