Good, so we're making progress. o)
Make sure to open the "script console" by choosing from the Help menu -> Logs -> Other Logs.
Then run this line by pressing ">" on your keyboard, pasting the following and pressing <enter>. Post the results.
SelectEx XLOG=all RANDOM FILES PATH="J:\00000000 Magicompilation\Pool" MAXSIZETOTAL=1000mb ITEMCOUNT=100 ECHO
I guess there are no files directly below the folder "Pool" or something's wrong with the SelectEx addin preparation/installation. ITEMCOUNT is something we can tackle later, I currently don't know if it's required when used in conjunction with MAXSIZETOTAL, it seems it should work without, not sure though.