Here's the story -

I installed Linux on my Y drive, and all went well until I tried to boot into XP again. I can't access or install an operating system to my other three hard drives, C, X, and Z.

I think that during the install my hard drives were changed to something other then NTFS, but Linux won't access them either.

When I use my Windows XP or Windows 7 disc, it says the drive has 0mb free, and it can't install until I delete the partition, then reformat. I don't want to do this obviously, because I don't want to format all of my data.

When I go to Places > My Computer it lists my CD drive, Filesystem, and the Y drive. It doesn't show my other three hard drives.

Under Palimpsest Disk Utility I can see my other three drives, but I can't access the data on them yet.

Help!

You don't say which Linux distro you installed or whether it was a "Live" version, it is possible you have created a system wide LVM.

If you have gparted installed see what it says about your disk partitions. If it's not installed try downloading the systemrescue cd from Main Page - SystemRescueCd (always useful to have) and see what gparted and the other tools have to say.

also, if you have a live cd, or if you can boot into rescue/recover mode on the CD do an fdisk -l (L) and send the output to us

Thank you for your replies so far....

To run a command as administrator (user "root"), use "sudo <command>". 
See "man sudo_root" for details. 

ubuntu@ubuntu:~$ sudo fdisk -l 

Disk /dev/sda: 80.0 GB, 80026361856 bytes 
255 heads, 63 sectors/track, 9729 cylinders 
Units = cylinders of 16065 * 512 = 8225280 bytes 
Disk identifier: 0x00ca89b7 

   Device Boot      Start         End      Blocks   Id  System 
/dev/sda1               1        9730    78148608    7  HPFS/NTFS 

Disk /dev/sdb: 500.1 GB, 500107862016 bytes 
255 heads, 63 sectors/track, 60801 cylinders 
Units = cylinders of 16065 * 512 = 8225280 bytes 
Disk identifier: 0x3de4bf44 

   Device Boot      Start         End      Blocks   Id  System 
/dev/sdb1               1       60801   488384001   17  Hidden HPFS/NTFS 

Disk /dev/sdc: 500.1 GB, 500107862016 bytes 
255 heads, 63 sectors/track, 60801 cylinders 
Units = cylinders of 16065 * 512 = 8225280 bytes 
Disk identifier: 0x76397639 

   Device Boot      Start         End      Blocks   Id  System 
/dev/sdc1               1       60801   488384001   8e  Linux LVM 

Disk /dev/sdd: 500.1 GB, 500107862016 bytes 
255 heads, 63 sectors/track, 60801 cylinders 
Units = cylinders of 16065 * 512 = 8225280 bytes 
Disk identifier: 0x32dbca08 

   Device Boot      Start         End      Blocks   Id  System 
/dev/sdd1               1       60801   488384001   8e  Linux LVM 

Disk /dev/sde: 80.0 GB, 80026361856 bytes 
240 heads, 63 sectors/track, 10337 cylinders 
Units = cylinders of 15120 * 512 = 7741440 bytes 
Disk identifier: 0xf03b4104 

   Device Boot      Start         End      Blocks   Id  System 
/dev/sde1               1       10338    78147584    7  HPFS/NTFS 
ubuntu@ubuntu:~$ 1

Ok you definitely have a LVM problem with hidden partitions.

try the following:

sudo mount -t ntfs /dev/sda1 /mnt/foo
sudo ls -l /mnt/foo
sudo umount /dev/foo