WTOS device do not have an Administrator account nor a user account, therefore there is no password. You can lock the administrative functions of the client via the WNOS.INI file, but you define the password by using the following parameters:
AdminMode=Yes \
Admin-Password=

You can find more details in the WTOS INI reference guide available at www.wyse.com\manuals

Roger Montalvo 
Visit our Dell Wyse Thin Client Knowledge Base and Manuals web site at www.wyse.com/KB
Visit our Dell Wyse PocketCloud Knowledge Base and Manuals web site at http://pocketcloudsupport.wyse.com/forums
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I have this problem

I recently received a shipment -  200 pcs of used  Wyse Tx0 from Germany

I have tried everything possible within my reach to unlock the admin / bios in other to reset to factory default. No way

I am seriously in a big loss if nothing can be done. 

Any body with useful information?

For BIOS you would need to contact support.  For the OS password (ThinOS, Windows, Linux), if it is not one of the default, then it is what the previous owner has set.

If the previous owner did not reset it to default, or factory erase the system then you would need to download a new factory image and leverage the USB firmware tool to flash the device to a factory default image.

#Iwork4Dell

You can't do that if USB boot is disabled in the BIOS, and you can't enable it because the password is set.

Use the "Fireport" password for BIOS, case sensitive.

I'm in the same boat, has anyone found a solution?   I have tried placing a jumper on the various pins inside, but no luck.  None are marked in any way to suggest a bios reset, I just figured it may work or it may brick.  Neither happened.   Is there a serial admin port?   I don't see the standard bios battery either.   I imagine there is some way to hardware reset this thing, but I have yet to find it.