What method should I use if Im going to crack a NT password, where I know the password begins and ends with certain charactors. Say for example these charactors were 666. Example:

could be 666pass666, or 666woohoo666

If I knew it followed this pattern, what program could i use to just brute force the unknown charactors?

If the password is LM, rainbow tables can crack very quickly.

We are an non-official gso team that generate this tables. You can reach us at
irc.governmentsecurity.org
#gso-chat
or
#rainbowcrack

Idd Rainbow Tables rule.

After a few months generating I have 20 Gb of tables. Most of the hasehs can be cracked in a few minutes.

Only precomputations consumes a lot of time.