Stuck in Legacy boot mode

[#1]

Hi
I was testing out some BIOS settings that I have on my Acer Aspire ES1-311 and stupidly went from UEFI mode to LEGACY mode. The laptop now doesn't boot and OS and says no bootable drive.
So I go back into the BIOS settings thinking it's just a simple change. Since I don't know the password  I'm unable to change any of the settings. So essentially I'm stuck.  I'm accessing the BIOS via F2 key.
I never knew the password and that I used the unlock key to access which I got from here https://bios-pw.org.
There wasn't much work saved on the laptop as most of it was on my Office 365 cloud.
Oh and yes I've tried the different boot options via F12 and they are all giving me the same 'No bootable drive'
Many thanks.
NE

[#2]

the usual method is to try a password three times and then use the code from the popup box in the site you linked to - didn't that work

[#3]

Resolved.
Opened the laptop up, removed the CMOS battery for 5-10mins and put back in again. 
All working now. I wouldn't be doing that again 
Thanks
NE

[#4]

About the same time as you.....I had a  similar problem.... 
I have formatted an HDD that came with this laptop ( less than a year ago ) with Win 8.1.....  and managed to install a new copy of Win 7 Professional, from a DVD.
on boot up..after the install was finished, Got the same message...
__________________________________________________________________________
No Boot Device Found. Press any key to reboot the machine...
___________________________________________________________________________
Pressing any key, just recycled the above message...... 
                                then I used the F12 key after the reboot had started, and this gave the message... (Starting one time boot option)  or similar... and the following
___________________________________________________________________________
use up and down arrow to select
Boot Mode is set to : LEGACY ; Secure Boot : OFF
Legacy Boot:
                    USB Storage Device
                    CD/DVD/CD-RW Drive
                      Internal HDD
                      On board NIC
UEFI BOOT
                  Windows Boot Manager
Other Options
                BIOS Setup
                BIOS Flash Update
                Diagnostics
                Change Boot Mode Settings
  When I selected the UEFI BOOT option  ( windows boot manager)... the laptop then booted as normal....  However,... subsequent re-boots mean I have to perform this ritual every time.





(that was written about the same time as the OP...... )
since then, I have done a few updates..... and in the past week,  the system just boots up normally...... I have not changed anything ( except as mentioned above..)

[#5]

haha cool 
Glad it fixed itself in the end.  Hated windows 8.1 and not too keen on Windows 10.  Preferred Windows 7 but obviously shows my laptop doesn't want that 
NE