UNMOUNTABLE_BOOT_VOLUME - Pk4 File

I'm in a world of hurt. I ran windows defrag on my machine which has a 160GB SATA hard drive. It's a Dell machine and I'd never run defrag on it before. I left the computer and came back to find it at 45% on some .pk4 file and went to bed. When I came back to it the next morning, it was still frozen at that so I stopped the defragmenter, closed it, and tried to reopen it but it was going realllly slow. So rebooted, and was greeted with a blue error screen with UNMOUNTABLE_BOOT_VOLUME and a buch of hex keys. So went through a lot of trouble but ended up installing an internal floppy drive so that I could run windows recovery console with the SATA drivers and the Windows cd. I got in (without having to enter a password or select by windows installation) and ran chkdsk /p. When it finished, it didn't do much, just told be how big the hard drive was and that it had errors on it. So I rebooted into windows to find out what the error code was, and for some weird reason it sucessfully booted into XP. It's still really messed up (hangs, crashes, etc.) but it at least boots up.