Don't know windows password.Here it is 

For cracking windows password
using Backtrack you should have
a Backtrack DVD. Insert DVD and
boot from it. Now Backtrack have
many offline password cracking
tools pre-installed, we will use
one of them.
Continue using following steps:
Step 1: Open
applications>Ba ctrack>Privileg e
Escalation>Pass word
Hacks>Offline Attacks>chntpw
Step 2: Type fdisk -l
Step 3 Type mkdir /mnt/apple
Step 4: Type mount -t ntfs-3g /
dev/sda1 /mnt/apple
Step 5: Type ./chntpw -l /mnt/
apple/WINDOWS/ system32/
config/SAM
Step 6: Type ./chntpw /mnt/
apple/WINDOWS/ system32/
config/SAM
Step 7: After you have the user
edit menu select the appropriate
step, here we have to clear
password so type 1 and press
enter
Step 8: Now it will ask for
writing hive files so type y and
press enter
Now your windows password
has been cleared. When the next
time you will login it will not ask
for password.