Invalid magic number 0000 in log file

Hi everyone,

    a customer reported an issue starting Postgres on his machine after
reinstalling Windows (10 before, 10 now) without formatting (so there's
Windows and Windows.old) because of Windows not starting up anymore.

Before this reinstallation everything was OK.

Now here's the log

2017-08-25 19:34:49 CEST LOG:  database system was shut down at
2017-08-25 08:37:08 CEST
2017-08-25 19:34:49 CEST LOG:  invalid magic number 0000 in log file 1,
segment 53, offset 0
2017-08-25 19:34:49 CEST LOG:  invalid primary checkpoint record
2017-08-25 19:34:49 CEST LOG:  invalid secondary checkpoint record
2017-08-25 19:34:49 CEST PANIC:  could not locate a valid checkpoint record

This application has requested the Runtime to terminate it in an unusual
way.
Please contact the application's support team for more information.
2017-08-25 19:34:50 CEST LOG:  startup process (PID 6652) exited with
exit code 3
2017-08-25 19:34:50 CEST LOG:  aborting startup due to startup process
failure

PostgreSQL is 9.1.6 32-bit. (I know, EOLed, but it's hard to keep up to
date about 1000 customer machines!)

I know that's related to XLOG files, but do not have idea on how to deal
with it. I had a quick googling but found nothing but "your files are
corrupted. You'd better initdb." Then I bumped into this (old) post from
Alvaro

https://www.postgresql.org/message-id/20070515173401.GB12731@alvh.no-ip.org

If it's  applicable, is it still valid or too many things have changed?

Thanks in advance,

Moreno.