how can i update hashcat on bacntrack ?

[mastercracker]

then where can i find the password i just crack!
root@bt:/pentest/passwords/hashcat# ./hashcat-cli32.bin -m 0 /root/md5.txt /root/passwords.txt

I don't know how you call the command line window in unix but it would have been printed there. An easier way for you would be to use the following in your command line:
-o found.txt

Once they are cracked, the Hash:password will be in found.txt