Appache http server stops working

Hi to all who read this,

I am a few weeks away from 80 and trying to help my son manage changes to his https wordpress site by copying it to my local server. So, be gentle as I am not used to forums.
I have copied his domain wordpress subdirectory, put it in the xampp htdocs folder of my local server and suitably modified the user name and password of its wp-config.php file. I have, using command line and by increasing buffer size, imported his sql database copy into my local server, created a user with full privileges to access the imported database and modified the options table of the database so that siteurl and home point to the localhost.
The local word press appears to access the database but then the apache server stops working. (It works fine with another local wordpress install). The apache error log says it exited with status 3221225477

My question is what could cause the server to stop and/or what actions might I take to try to resolve these difficulties. I have so far set wp-debug to work and its log tells me an rss plugin php is declaring deprecated insensitive constants. Can that have anything to do with the server shut down?

Regards and thanks in advance
Auldbert