Corrupt Hard Drive

Basically, my external hard drive was being bitchy and reporting corrupt data. So I try and run chkdsk /f on it. I leave it on for 24 hours and the drive is still unreachable, apparently due to chkdsk, but it didn't seem to be running when I checked the processes list.
Rather stupidly, I pulled the plug on the drive and I think I'm now screwed. It's now reporting that the drive is corrupt and unreadable and I can't seem to do anything about it. Chkdsk won't run.
What can I do? I really do not want to reformat the drive.

What type of drive is it, SATA or ATA (or something else :p)?

If it's a SATA drive, as long as it's not the drive you boot from and you didn't pull it out in the middle of an important write operation then you should probably be ok, since SATA drives are hot-swappable. If it is the drive you boot from then you still may be ok. I've seen this happen before and all that happened was that Windows slowed down and locked up after a while - the drive was fine on reboot.

If it's an ATA drive you're going to have a hard time recovering data from it (I'm assuming you pulled the plug while the drive had power supplied to it. :p). When the power cable to my old ATA fell out, it busted up my filesystem (or at least the first few sectors of it), so the drive was no longer mountable. I had no luck with any free utilities in re-forging the FS, but I did have limited success with Encase (which is an expensive data forensics utility). :p

It could be difficult even just to format it - I recommend trying to check and then mount the drive by booting off of a Linux live CD, just to see where you're at.

If you don't have any luck accessing the drive and further posts in this thread don't help/work either, you can always check into shops in your area that specialize in data recovery, although they can be pricey.

I haven't got a clue what type of drive it is. As far as I know it's a USB external HDD. I think I pulled the power plug out first. How would I find out whether it's an ATA or a SATA?

Edit: I was able to rerun chkdsk /f from the command line and I appear to have saved 40GB out of 400GB. Any one got any ideas if it is in anyway possible to get the remaining data back?

Edit 2: Ah sod it. Looks like the data's gone. *sigh*

Now my HDD seems to be randomly losing data and I have some undeletable empty folders. I've really messed it up now. What I want to know is: will reformatting the drive completely help in any way?
I've run chkdsk /r and that didn't help and I don't have enough money to buy a replacement.

Format if you've got undeletable items on the disk and chkdsk's not fixing it (and it's not a security/permission problem, which is unlikely on a home machine), it usually means something very bad has happenned to the file allocation tables :p Copy stuff off it first though, and full format just to be sure if you want to :p

I'm currently copying off stuff I want right now. I lost most of the data when it crashed last week so it isn't much.