From this link above I used the script that retrieves the print processors to a text file, that enabled me to see if any print queue has a print processor different than Winprint.
Then I ran the script below the first script to change all the print queues print processor to Winprint, and dump the result to a text file, so I did and viewed the result text file and it showed that all the print queues have their print processor changed to Winprint.
However, by chance I went to print cluster and checked some print queues and found that they have not been changed to WinPrint.
I don't know what went wrong.
Any idea ?