Ok, I screwed up. The long and the short of it is I formatted a partition on a system that the bios could not handle the size of the drive.

This drive is an IDE 300gig Western Digital. Has/had a 50gig NTFS partition and another 250gig NTFS. In my haste, replaced the motherboard with one who's BIOS apparently cannot read such large drives. I began to install XP on it, and it saw the different partitions, just considered them damaged. Anyway, I formatted the 50gigs before I realized what was going on.

My question is - if I slave the drive on a Linux machine, will an application like GPART help me fix things long enough to get the data on the 250gig partition off the drive? Or is there another solution? Just how screwed am I? I will learn HEX if that's what it takes

You will be better off with windows tools trying to recover that data. If the partition was just deleted or reformatted with no data written to the drive, You should be able to get it back with some of the widely available data recovery tools.

The best freebie one is PC Inspector:

http://www.pcinspector.de/file_recovery/uk/welcome.htm

The best for pay one I've found is Ontrack Easy Recovery:

http://www.ontrack.com/easyrecoverydatarecovery/

But it's not cheap($200 for the home edition). However, they have a free trial version that will tell you what it can recover if you by it. Ontrack is pretty much the Cadillac of the data recovery software available

Another more modestly priced one that I've heard good things about but never used is GetDataBack($80):

http://www.runtime.org/buy_now.htm

The critical thing is to make sure no data is written to the drive you want to recover data from. The more data that was written to it, the more problems your likely to have.

Thanks so much for the help! I'll check all those out!

Yeah - that's the thing. I'm not exactly sure just what got written over - it was just going to format 50gigs, but if it didn't know where the 50 began and ended - God only knows what happened. I'm keeping my fingers crossed that it only messed with the 50gigs and only the File Allocation Table got wiped out.

-=[EDIT]=-
If money were no object - what's the best choice? And will trying with one mess up another attempt with another application?

If moneys no object, the Ontrack one is the way to go. I believe they also have a service which will recover the data for you for a fee. But again, it's not cheap.

If you have a spare drive with lots of space, apparently 300GB of free space or a blank spare drive of the same or greater size, you can do a sector by sector backup of your damaged drive to it in linux using the dd command:

# dd if=/dev/<device file of damaged drive> of=/dev/<device file of backup drive>

You can even back it up to a file with:

# dd if=/dev/<device file of damaged drive> of=/<path to directory to store image file>/file_name.img

That way you can fool around with the drive to your hearts content and not worry about losing anything although the tools should not do anything to the drive itself. But I can't guarantee that.
Be advised that it takes a long time to run this software; I had to recover an 8GB partition with PC Inspector and it took 12 hours but I got my data back. You can try Ontrack's free version to see what data it can get; it should run faster than PC Inspector as it's a professional tool. Running the dd command on a 300GB drive will also take a long time so be prepared for that.

Formatting and partitioning operations are usually no problem to recover from because the data is still there. Those operations just mark the sectors on the drive; they do not overwrite data. If data started getting written to the drive, that's when you start having trouble.

Very Cool.

If I use Ontrack, (or PC Inspector for that matter), will I be able to copy things out piece-meal? Or will I be restricted in how I can get the data off the drive?

This would give me time to pull stuff off and burn it, heheh.

It's been a long time since I've used either tool but I don't believe so. I'd try PC Inspector and if that doesn't work or is taking too long, try the trial version of Ontrack and see if it can do the job faster/better. See what Ontrack can recover and decide if you want to pay for it.

You may not be as screwed as you think.

If you are lucky, the 250 GB partition whose data you care about wasn't touched. If so, you can access it using a bootable Linux "live" CD such as Knoppix & copy it to safety.