Tally has 2 types of Password, it is stored in Company.500 or Company.900 file.
1. First type requires UserName & Password, it can be recovered, by making a dummy company, then using with password protected company.
2. Second type, is called Vault Password, very difficult to recover, as it is protected by DES algorithm. If we used brute force method then also it will take around 25 yrs to get your password.
There are many commercial site, for password recovery.
*www.tallypassword.com