Merging /home partition into / partition

["Anurag Jalan" <a_jalan vsnl com>]

Hi all,

On my server's 1st hard drive I have 3 non-swap partions

/ sda             ( 63 % used )
/boot            ( 6 % used ) 
/home  sda4 ( 73 % used )

I want to move my /home to a new HD /dev/sdb
I partitioned /dev/sdb into a single partition /dev/sdb1
Mounted /mnt/disk2/home on /dev/sdb1 in fstab
did a cp -a /home/* /mnt/disk2/home/

At this point i am getting stuck :( 
/home contains all my SAMBA and Apache directories .
I want to merge the present /home partition with / .
I tried to rm -r /home and create a link :
ln -s /mnt/disk2/home /home , but Linux says, that /home is
not a file or directory .. what should I do ?

Regards
Anurag