After 2 days both in Day and night, I have installed both Windows 7 and Backtrack 3 and Dual Boot them Successfully!The procedure is as follows:

Before that, you should get ready for these:
(1) backtrack 3 livecd
(2) installed Windows 7 on HDD firstly.
(3) Always write the error information with your pen and paper, then search the resolution from the internet esp. backtrack-linux.org and their official website.
(4) knowledge, patience & careful

1. umount all the ntfs,ext2,ext3,vfat,reiserfs partitions
umount /dev/hda1,3,5,4,6,7
2. fdisk d # delete partitions
fdisk /dev/hda
d # delete
7 # delete hda7 partition
d
6
d
4
w # save
init 6 # reboot
3. fdisk n # create partitions
fdisk /dev/hda
n # create a new partition, give start cylinder & end cylinder
7690
8686
n
8687
9600
n
9601
9729
4. make swap partition
t
7
82
a # define the boot disk for linux
7 # linux boot partition hda7
w # save

5. format
mke2fs /dev/hda7
mkswap /dev/hda8
swapon /dev/hda8
mkreiserfs /dev/hda6

6. copy & setup
mkdir /mnt/backtrack
mount /dev/hda6 /mnt/backtrack
mkdir /mnt/backtrack/boot
mount /dev/hda7 /mnt/backtrack/boot
cp --preserve -R /{bin,dev,home,pentest,root,boot,usr,etc,lib,opt,sb in,var} /mnt/backtrack
cd /mnt/backtrack
mkdir {mnt,proc,sys,tmp}
chmod 1777 /mnt/backtrack/tmp
mount --bind /dev /mnt/backtrack/dev
mount -t proc proc /mnt/backtrack/proc/
chroot /mnt/backtrack /bin/bash
7. modify lilo.conf
nano /etc/lilo.conf
lba32
boot=/dev/hda
prompt
timeout=60
change-rules
reset
vga=791
image=/boot/vmlinuz
root=/dev/hda6
label = backtrack 3
# windows 7
other=/dev/hda5
label=windows 7
table=/dev/hda
8 save lilo
lilo -v
reboot
mkdir /mnt {hda1,hda3,hda5,hdb1,sr0}
9. modify fstab
nano /etc/fstab
init 6
10.use windows 7 setup cd repair the boot mbr
#might need to do this: bootsect.exe /nt60 ALL /force /mbr
11.#only for test grub usage purpose in my environment , which might be useless for you:
windows 7
rootnoverify (hd0,0)
makeactive
chainloader +1
boot

root (hd0,7)
kernel /linuz root=/dev/hda7 ro vga=791
boot

12.Finished!!