If the PostgreSQL server won't start at all, because its transaction logs are damaged, you will probably need to recreate the database store totally.
To rebuild the database:
bin\initdb -D <VPOP3folder>\pgsql\data -U postgres -W -A md5
copy data_old\postgresql.conf data
copy data_old\vpop3db.conf data
copy data_old\vpop3dbuser.conf data
to copy the database server configuration to the new location. You may be prompted if you want to overwrite the existing file. If so, confirm the overwrite.
createuser -S -D -R -U postgres -P vpop3
At the 'Enter Password for new role' and 'Enter it again' prompts type vpop3pass. At the 'Password:' prompt type pgsqlpass (or whatever password you defined in the step 4 above)
Once you're happy everything is working OK, you can delete the data_old folder.
The most common causes of this type of corruption are some third party software accessing the pgsql\data folder files - usually a virus scanner or backup or file synchronisation program. Backup programs using the Windows 'volume snapshot' (VSS) service are OK to access the pgsql\data folder, other backup programs should always be excluded from the pgsql\data folder.
Note that if you use a backup program which doesn't use VSS, even if it does a copy of the pgsql\data folder without causing any problems, that copy will not be usable, so there is no point doing it. See here for how to backup the database correctly
The only files in the pgsql\data folder which should ever be accessed by anything other than PostgreSQL itself are the contents of the
pg_log folder (NOT the pg_xlog/pg_clog folders!) or the
You may be able to use the pg_resetxlog.exe program to create new transaction logs and control files which are 'just good enough' to get PostgreSQL started again, then you can backup the database before doing the following steps. (Do not use pg_resetxlog.exe, then continue using the database without doing a full backup/rebuild/restore, corruption may be hidden, and cause bigger problems in the future). See the pg_resetxlog instructions for details on how to use that utility.