Have one of the Cache Flow 645 systems and got it from another and need to know how to reset the admin password on this device or take it to default settings so we can use this please.

The CLI uses two passwords: The CacheOS or CacheOS Server Edition console
password is required to establish a connection to the interface, and the enable password
can be set to restrict access to the privileged mode configuration options. If you have
forgotten the username or password, you can reset them by using the Setup console.

Dear Sir,

Is there anyone here can solve my problem to reset user & passwd of cacheflow ca645, i did all things but still no clue, i use pc with windows 7 and connecting with serial cable via hyper terminal.
If someone know and willing to help me, please kindly inform me to my email dosimple@rocketmail.com. Thank you.

Only a reinstall of the OS can help you do what you want to. That is the problem with all passwords that once you loose/forget them, you have to reinstall the OS thus destroying the data that you wanted to protect. You still have a chance of protecting your data by backing it up now before you reinstall the OS. Even if you back it up on the same HDD as the OS it does not matter as only the OS will be touched, including the My Documents/Pictures/Videos and the like. So, backup the data and reinstall. Alternatively, go to Start->Control Panel->User Accounts->Create new User. And create one with admin rights say XYZ. Login as XYZ and try to delete the Admin user. It may be possible (at least theoretically). Unless you try it you can not be sure whether it works or it does not.