Had Win XP and Gentoo dual-booting fine with grub.

Ran out of space for Gentoo (it was on an older laptop, only 10 gb hdd). So, I booted into winXP, and used Partition Magic to add more space to the linux root partition (it was at the very end of the drive, so I shifted everything forward).

Upon restarting, Grub gave an error 17.

Booted into gentoo liveCD, tried to reinstall grub, but grub gives an error when I try to specify the boot drive... It says unrecognized filesystem (even though I can mount and access the partition just fine).

Any suggestions?

Alright. I don't know what went wrong (I can only assume partition magic messed up my MBR...), but here's how I fixed it:

Went into fdisk, changed the partition type of my boot partition to 0 (empty), saved changes. Restarted (maybe not necessary), went back into fdisk and change the type back to 83 (linux). Re-emerged grub, and set it all up again the way I had the first time. Now it works.

Well, from my experience every time that you use Partition magic, the mbr is changed or corrupted or whatever somewhat. I don't know about the rest though because just reinstalling the bootloader on the mbr is what fixes it for me.

I've used it once before and had no problems. Maybe I didn't move things around as much, I don't remember.

I thought reinstalling would be all that was needed, but for some reason grub didn't recognize the partition type (it gave an unknown filesystem type error).

The main thing is I fixed it.

Well, as far as I know, things will only be affected if you resize the windows partition which the program is on and you have to go through the rebooting procedure.

But, as you said, the only important thing is that you fixed it.