I have the same error but cannot locate these keys in the registry. I had previously installed AVG but it it completely removed (according to the removal tool).
Bootstrap log:
26-5-2017,13:25:59,Information,------------------ Beginning installation of Sophos Anti-Virus and AutoUpdate ------------------,
26-5-2017,13:25:59,Information,Setup version 3.1.5.29,
26-5-2017,13:25:59,Information,Command line: c:\users\familie\appdata\local\temp\11afcf39-33ab-4b16-9954-dbbe5ee7175e\setup.exe -server dzr-mcs-amzn-us-east-1-h0m3.upe.p.hmr.sophos.com -token ***************** -producttype 1,
26-5-2017,13:25:59,Information,Process security set successfully,
26-5-2017,13:25:59,Information,Setup program was run from C:\Users\Familie\AppData\Local\Temp\11afcf39-33ab-4b16-9954-dbbe5ee7175e,
26-5-2017,13:25:59,Information,Checking if Sophos Anti-Virus or Sophos AutoUpdate are installed...,
26-5-2017,13:25:59,Information,Starting wizard to collect information from user...,
26-5-2017,13:26:01,Information,Starting the install sequence.,
26-5-2017,13:26:01,Information,Checking for internet connectivity...,
26-5-2017,13:26:01,Success,Successfully connected to the URL http://dci.sophosupd.com/.,
26-5-2017,13:26:01,Information,Checking for internet connectivity...,
26-5-2017,13:26:02,Success,Successfully connected to the URL dzr-mcs-amzn-us-east-1-h0m3.upe.p.hmr.sophos.com/.../ep.,
26-5-2017,13:26:02,Information,Checking for local third-party software...,
26-5-2017,13:26:02,Information,SophosFeedbackData threw exception: Could not connect. Error code = 0x800700c1
,
26-5-2017,13:26:02,Information,Done.,
26-5-2017,13:26:02,ERROR,There was an unexpected problem with the installation of Sophos Home. Details: Could not connect. Error code = 0x800700c1
,
26-5-2017,13:26:04,Information,Sending EBS feedback to Sophos...,
26-5-2017,13:26:04,Information,Sending data back to Sophos...,
26-5-2017,13:26:04,Success,Successfully connected to the URL d1.sophosupd.com/.../x.xml.,
26-5-2017,13:26:04,Information,------------------ Installation program finishing with code 124 ------------------,
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