Instructions
Locate and open the "Touhou" game folder on your computer. In most cases, the file will be located in the "C:\Program Files" directory.
Open the "vpatch.ini" file with a text editor. Locate the "GameFPS" line and change the numerical value to one that is lower than 60. The lower the GameFPS number, the slower the game will run.
Click "File" and select "Save" to save your new settings. Open the "Touhou" game and begin playing as usual.