winrar - Password Strength Calculator

We want to recover unknown password from Windows XP machine. We don't want to reset it because we hope that with this password we can access another accounts. We already tried Ophcrack LiveCD but we didn't succeed. The password may contains some Czech specific characters. What else should we try?

Note: This isn't some illegal activity I want just help to my friend to take over business of his deceased father.

Give Windows Password Cracker a try. Supports international character sets.

You can always crack the password as others have mentioned.

If you just need to get in to access some stuff temporarily... one method I used a long time ago... is booting to the recovery console... and then copying these files to a temporary location...

copy c:\windows\system32\config\system c:\windows\tmp\system.bak
copy c:\windows\system32\config\software c:\windows\tmp\software.bak
copy c:\windows\system32\config\sam c:\windows\tmp\sam.bak
copy c:\windows\system32\config\security c:\windows\tmp\security.bak
copy c:\windows\system32\config\default c:\windows\tmp\default.bak

Then I used a password reset tool to change the account password. Then I restarted, logged in with the new password and perform what I needed to get done. Once I was done, I restarted into the recovery console again and I restored the old password by doing the following...

delete c:\windows\system32\config\system
delete c:\windows\system32\config\software
delete c:\windows\system32\config\sam
delete c:\windows\system32\config\security
delete c:\windows\system32\config\default

copy c:\windows\tmp\system.bak c:\windows\system32\config\system 
copy c:\windows\tmp\software.bak c:\windows\system32\config\software 
copy c:\windows\tmp\sam.bak c:\windows\system32\config\sam 
copy c:\windows\tmp\security.bak c:\windows\system32\config\security 
copy c:\windows\tmp\default.bak c:\windows\system32\config\default

Of course, YMMV... but it worked for me.

The commercial LoginRecovery website might be worth a try:

Just use the box below to download the utility. This is a ".exe" file which will burn itself onto a blank CD. Then pop the CD into your locked PC, and boot from the CD.

If you have an Internet connection on your locked PC then it will automatically upload the encrypted password to our server for decryption. Once decrypted, we will send you an email advising you where to log in to view your Windows password.

If you don't have an Internet connection to your locked PC, you can extract the encrypted password to a USB stick and upload manually to our website for decryption.

Any chance there is a lanmanager (or is that NETBIOS?) version stored someplace? Those are trivial to brute force. I don't know if there is, but if a copy is stored someplace (on another machine perhaps? OS X accounts created 10.4 or earlier created them by default, even if not used, for example).

Ophcrack may work if you can get the right rainbow tables. The free version has a limited table, but contact the maker and see if he or she can sell or give you a wider set of characters.

Additionally, if Ophcrack will show you the NT Hash and the LM hash, I think there are websites to decode those hashes. I'm not sure if it's free or what, but you haven't reached a dead end with Ophcrack unless you've used the full version.