Sounds like you would be better off installing grubs' 1st stage to the boot sector of the root partition that you have Mepis installed to. As long as it is within the range of the bios, all you would then need to do would be to set the Linux partition active/bootable, and then have an appropriet entry for your windows install in the /boot/grub/menu.lst file.
But then, i think that will just repeat the experiance you just had and so it probably wont be just as simple as that.
Unless there is some peculiarity about the bootstrap that XP writes.In any case, if after doing that, and setting the Linux drive bootable/active via cfdisk/fdisk, it was to again disable your F10 key, then just reseting your XP partition active would fix that.
Assuming it is the XP partition that is set active. Maybe it's the hidden partition that is really set as the boot partition, and it just jumps to that and then jumps up to XP, unless the F10 key is pressed. One way to find out, could you run ...
]# cfdisk -Pt /dev/hda
(or what ever the device name for youd drive ... sata would be sda)
And post the result ... it will show just what the partition layout is and which is actually being set as bootable. That would be a big help in visualising this.
As far as getting grub onto the Linux partition boot sector, just boot a LiveCD, to the console and rerun Grub, as such ...
grub> root (hd0, 1)
grub> setup (hd0,1)
That would tell grub to use the secondary boot files found on the first drives second partition. That is, the /boot/grub directory is on that partition. Then it would install grubs 1st stage loader to the boot sector of the same partition.
You would then need to set the table entry bootable with fdisk/cfdisk.
I suspect though, that will likely disable your F10 key again, but easily reversible by reactivating your XP partition with cfdisk/fdisk. If that is the way it eventuates, then you would have to make a copy of that linux bootsector, using 'dd', and then just copy the image made over to the root of your C: drive/partition. With a subsequent entry made for your Linux install added to your 'boot.ini' file. Which will likely be hidden unless you have enabled 'show hidden/system files' in XP.
It seems the ntldr system will invoke other OSes, but it must be able to find their respective 1st stage loaders in its' own C: drive root. And have a 'boot.ini' entry.
I haven't had the need to do that myself but a few people here have, and have posted some good discussion on the technique. So a good search around on 'boot.ini/ntldr/dual booting ntldr' etc should find those posts.
It isn't that complex, all you basically need to do is install grubs 1st stage to the Linux bootsector so that it has the appropriate mapping to its' secondary files. Copy it out from there to a file (grub-1st.img), then copy that 512 byte file over to the XP C: drives root, and then make an entry in the boot.ini file.
The only real thing to watch there would be 'dd'. Have a really good read up on the man and info pages first as it can be a very unforgiving program. Get its' input/output switches back to front and it will flatten whatever it was pointed at. Otherwise it's a gem.
Do post that cfdisk output, as it would be helpful to just see just how the layout is.
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