I've checked the quotation marks, and tried upper case / lower case, removing the examples for other operating systems. I've even overwritten the config-dist.php file from a new extraction of the zip file and started again.
Like Ian, I've spent a whole day on this - the urge to hurl the computer across the room is getting stronger ...
Any suggestions, anyone?
Notice: Undefined property: dirroot in c:\program files\easyphp1-8\www\moodle\config.php on line 272
Notice: Undefined property: dirroot in c:\program files\easyphp1-8\www\moodle\config.php on line 275
Error detected in config.php
Notice: Undefined property: dirroot in c:\program files\easyphp1-8\www\moodle\config.php on line 280
Error in: $CFG->dirroot = '';
Try this: $CFG->dirroot = 'c:\program files\easyphp1-8\www\moodle';