In Windows, what should I set //$pathToFiles='./'; variable to?

'./' does not work.
Location of the folder is C:\miniBB.

I've tried different combinations of single/double quote/slashes and nothing seems to be working :( Any help would be apprecaited.

Did you try C:\miniBB ?
I'm not sure if that would work because I do not use a windows server but that's the path you described, so it might.

I use the same setting

$pathToFiles='./';

both for my localhost server (Windows) and Linux server within my webhosting and it works in both cases. What lead you to the idea that particularly $pathToFiles is set wrong?

miniBB manual says:

Pay attention also at the option $pathToFiles, which is described below. It's not subject to change, if you're not having any difficulties with running the board. However, on some operating systems like Windows, and some server configurations, it will be strongly required, that you set full absolute path to your scripts, so they can be included via PHP's include function properly. Also, many third party libraries functions available in PHP, require this option to be set as full path (GD or Aspell, for example).

(similar observation to lime's) and also make sure that you do not have the line commented, i. e.

//$pathToFiles='./';

is wrong, it should look like

$pathToFiles='./'

As suggested you may try both

$pathToFiles='c:\miniBB\\';

or

$pathToFiles='c:/miniBB/';