GnuCash delete backup and log files
Solution 1:
If you want them to be removed automatically, Gnucash can remove them after a configurable amount of time (Preferences > General > "Days to retain log files").
Another chance would be to write a batch file to remove .xac and .log files inside the relevant directory.
You should notice that the backup and log files have a format of <name>.YYYYMMDDHHMMSS.xac (or .log). These are backup (and log) files from your data file, <name>.