My computer falsely reads an HDD as in a raid, what should I do?

I formerly had a stripe raid set up on my computer, but since then I have disabled it. Since then I have removed one of the disks that used to be in the raid (had bad sectors), and replaced it with a bigger drive of the same series. Everything was fine until I took my comp apart and put it into a new case. Now my main drive works just fine, but the drive that was formerly part of that raid is being read twice as big as it should be, and it’s being listed as exactly half full. I can’t read any files on the disk.
I’m running xp sp3 if that helps.
My bios is set to configure sata as IDE, so I know that’s not the issue.

Any ideas? Thanks in advance!