Comp has trouble identifying new harddrive?

Screwed up XP on my old harddrive. Got a brand new harddrive.

Initially had some difficulty getting the computer to recognize the new hard drive; I had apparently plugged it in to the wrong slot on that cord, if memory serves. Switched the plugs, worked fine.

Installed windows. Successfully slaved the old harddrive to the new one, where I could use both in windows XP [Old drive became "F:\"]. Started installing a handfull of things, namely drivers and a couple games. Was running fine for about a week. [If it matters, it was largely still running during that time, with a handfull of shutdowns due to having to install stuff like Direct X.]

Ten minutes ago, I decide I wanna play morrowind, which is located on the old drive. Exited out of the game I was playing, went to My Computer... and the slaved drive wasn't there.

Figuring it was a glitch, I rebooted the computer, only to find out that it isn't recognizing the new hard drive again.

Attempting to reinstall windows [again] reveals that windows is in fact still there on the new hard drive, which doesn't make much sense to me; how can BIOS not know what's attached to it, yet XP can read from it?

Anyway, I have two questions;  one of which being WTF.

The other question is... well, I was told to delete the windows directory on the old harddrive. I didn't.

Could having the old instalation of windows on the old [slaved] drive messed with the installation on the new drive?

At some point, a man's gotta concede.  Tip the piece over and shake the hand of your opponent.

In other words, try to recover whatever data you can, and set those two drives aside as suspicious trash.  Hard disks are fortunately cheap and for another 30 bucks or more, you'll get past all this.

When a hard disk is appropriately jumpered Cable Select and slapped on the cable anywhere, then the BIOS should see it without any problems.  Again, if you still want to confirm any of that, just simply the system (get rid of all other IDE devices and confine yourself to IDE0 and the end plug) and then work your way "up" (i.e. more complexity) from there.  Computer work is a matter of making simple, confirmed changes, one step at a time.  As soon as you assume, or take two or more steps at once, you're risking missing a problem or configuration and then you'll suffer.

Trashed computer stuff looks every bit as functional as the working stuff.  THAT's why you have to be methodical.