I'll try to help. You installed to /mnt/hda3. /mnt is usually reserved for mount points to mount partitions, devices, etc., and not used as a directory in which to install software. hda3 should be listed in /etc/mtab if it's a mounted partition or device. If it's not in mtab, look in /etc/fstab. If you find it there, but not in mtab, it's available to mount. The line in fstab should begin with something like '/dev/hda3' which you may have pointed to the mount point /mnt/hda3. So the line in fstab would read '/dev/hda3 /mnt/hda3' which means mount the device /dev/hda3 on mount point /mnt/hda3. You can then mount the partition like this: mount /dev/hda3 (specifying only the device to mount), or like this: mount /dev/hda3 /mnt/hda3 (specifying the device to mount and the mount point).
You can try to reinstall, but this time ./configure --prefix=/usr/local or some other directory in which to install (instead od mount point).
NOTE: by trying to install to the partition as in your first attempt, you may have overwritten the raw partition. If so, I hope there wasn't anything important there.