Hard-drives Apparently Corrupted After Attempted To Install A Second Hard Drive?

make a dualboot comp by adding windows XP to a new partition. I created the new partition with 20gb. (From the 500 of my actual harddrive)But before I actually installed on that, I got distracted with a second harddrive that my dad got(for no reason). It had a full copy of Windows XP backed up on it from another computer, so I figured I would just use that for the dualboot. I plugged it in (wired the same way as my old harddrive, but different data slot), restarted, checked the harddrive in explorer - all the data was there / reading correctly / etc, and I used 'easyBCD' to add the new harddrive to the boot list.(Which, of course, crashes if I try to start it. I just wanted to see what it would do). For a reason I can't remember, I unplugged the second harddrive for a bit, started the computer on accident (I don't know if anything loaded before I shut it off), and then when I plugged it back in.Windows 7 would not launch. It goes to a DOS-like window, except it's just a flashing _ and it never does anything even after a few minutes. XP didn't work still.. so I decided to reinstall XP (as I couldn't tell which harddrive was which on the list, I unplugged the main harddrive while installing onto the new).. and when I did this.. it formatted and installed fully... then restarted.. then restarted.. and restarted.. and just kept restarting, never showing any thing past the manufacturer logo/BIOS load-button-message-thing. So, I then try to use my 3-disk Windows7Recovery disk(burned myself with a program apparently included by the manufacturer.) It installed fully, appearing to work.. but when I launched it, it said "Invalid Partition Table" and wouldn't boot past that. When I insert my driver installer disk, it gives me a basic DOS window thing. dir A: shows the files in the disk. dir B: for some reason shows the same. C: says "Error reading from drive C: DOS area: general failure". All other letter:'s just say "invalid drive". (I'm doing this with both harddrives in.) I attempted connecting the harddrives to an old computer, but it gave an error for both. (It detected the harddrives, but said it had an error reading from it. Windows Explorer asked me to format it... {i'm willing to format one of the drives if anybody thinks it will help, but the old harddrive has data I'd prefer not to lose.} ) Looking on google, I saw several problems that all have similar problems (less overdescripptive than I am though) but none of the fixes suggested worked for me. Also - as I have two different with different errors, I only need to make one of them work.)Also - my other available computer has a CD burner / floppy drive if either are required. I also have several USB's. The computer can boot from USB's and CD's (tested), and I could easily take the floppy thingy and connect it to the computer.also - this computer is probably still under warranty unless unscrewing the hard drive voids it. .. does that count as modification of the computer?