You don't need to reinstall, just do:
mkdir /mnt/newhome
mount /dev/hdaX /mnt/newhome (where X is the new partition)
cp -a /home/* /mnt/newhome/
mv /home /oldhome (you can delete the oldhome later)
umount /mnt/newhome
mount /dev/hdaX /home
edit /etc/fstab to mount /home , this is what I have:
/dev/hdb6 /home ext3 rw,auto,users,exec 0 0