HP (Hewlett-Packard) Compaq Tablet PC ユーザーズマニュアル

If the tablet PC you are servicing has an unknown password, 
follow these steps to clear the password. These steps also 
clear CMOS:

1. Prepare the tablet PC for disassembly (refer to 

 for more 

information).

2. Remove the real-time clock (RTC) battery (refer to

 for more information on 

removing and replacing the RTC battery).

3. Wait approximately 5 minutes.

4. Replace the RTC battery and reassemble the tablet PC.

5. Connect AC power to the tablet PC. Do not reinsert any 

battery packs at this time.

6. Turn on the tablet PC.

All passwords and all CMOS settings have been cleared.