https://community.sophos.com/products/sophos-cloud/f/sophos-central/75044/re-register-computer-issue—no-tamper-protection-password

Tried this and it worked for me:

PHASE1:

To recover a tamper protected system, you must disable Enhanced Tamper Protection.

Do the following:

Boot the system into Safe Mode.

Click Start > Run and type regedit and then click OK.

Go to the following location in the registry editor:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Sophos MCS Agent and set the REG_DWORD Start to 0x00000004

Go to the following location in the registry editor:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Sophos Endpoint Defense\TamperProtection\Config

Set the following DWORD values to 0: SAVEnabled and SEDEnabled

Reboot the system in normal mode.

Taken from Article 124377

PHASE 2

Then I went to uninstall and got an uninstall error so I created a batch file with the following:

net stop “Sophos Anti-Virus”
net stop “Sophos AutoUpdate Service”
:Sophos AutoUpdate
MsiExec.exe /qn /X{7CD26A0C-9B59-4E84-B5EE-B386B2F7AA16} REBOOT=ReallySuppress
MsiExec.exe /qn /X{BCF53039-A7FC-4C79-A3E3-437AE28FD918} REBOOT=ReallySuppress
MsiExec.exe /qn /X{9D1B8594-5DD2-4CDC-A5BD-98E7E9D75520} REBOOT=ReallySuppress
:Sophos Anti-Virus (Endpoint)
MsiExec.exe /qn /X{8123193C-9000-4EEB-B28A-E74E779759FA} REBOOT=ReallySuppress
MsiExec.exe /qn /X{36333618-1CE1-4EF2-8FFD-7F17394891CE} REBOOT=ReallySuppress
:Sophos Anti-Virus (Server)
MsiExec.exe /qn /X{72E30858-FC95-4C87-A697-670081EBF065} REBOOT=ReallySuppress
:Sophos System Protection
MsiExec.exe /qn /X{1093B57D-A613-47F3-90CF-0FD5C5DCFFE6} REBOOT=ReallySuppress
:Sophos Network Threat Protection
MsiExec.exe /qn /X{66967E5F-43E8-4402-87A4-04685EE5C2CB} REBOOT=ReallySuppress
:Sophos Health
MsiExec.exe /qn /X{A5CCEEF1-B6A7-4EB4-A826-267996A62A9E} REBOOT=ReallySuppress
MsiExec.exe /qn /X{D5BC54B8-1DA1-44F4-AE6F-86E05CDB0B44} REBOOT=ReallySuppress
:SDU (1.x)
MsiExec.exe /qn /X{4627F5A1-E85A-4394-9DB3-875DF83AF6C2} REBOOT=ReallySuppress
:Heartbeat
MsiExec.exe /qn /X{DFFA9361-3625-4219-82C2-9EF011E433B1} REBOOT=ReallySuppress
:Sophos Management Communications System
MsiExec.exe /qn /X{A1DC5EF8-DD20-45E8-ABBD-F529A24D477B} REBOOT=ReallySuppress
MsiExec.exe /qn /X{1FFD3F20-5D24-4C9A-B9F6-A207A53CF179} REBOOT=ReallySuppress
MsiExec.exe /qn /X{D875F30C-B469-4998-9A08-FE145DD5DC1A} REBOOT=ReallySuppress
MsiExec.exe /qn /X{2C14E1A2-C4EB-466E-8374-81286D723D3A} REBOOT=ReallySuppress

Run that

PHASE 3:

It was still showing up in the Control Panel/Uninstall Programs which prevented installation again. Run Microsoft’s fix it:

https://support.microsoft.com/en-us/help/17588/fix-problems-that-block-programs-from-being-installed-or-removed

Choose Sophos and uninstall.