so what happens is when i add effects or transitions i cant play it with the preview, but when i export the video and watch it the video seems to be okay. I still want to kno how to fix it so that i can see the preview before i export
Sounds like your graphics card isn't up to task. Open up the program settings in Movie Edit Pro. (This is for version 14 - you didn't mention which version you have, but if it's different, it should be similar.) Under the "Video/Audio" tab, under "Video options", untick the box for "Hardware acceleration". You will need to reboot your computer for this to take effect.