dimossboy,

If by 'drag' you mean slow and stuttery playback in the preview window, the most likely problem is computer power. What are your system specs? An incredible amount of processing is going on to create transitions and effects on the fly. There are lots of variables but high definition & highly compressed source material can be a problem, and previewing full screen at best quality will make things worse.

My typical setup is previewing a half size (right click for 'Resolution presets' in the preview window) and at half resolution (under 'Movie display' on the video/audio tab of 'File' >> 'Program Settings' -- [Y] key shortcut. For previewing really complex stuff I move along using the cursor keys. Playback is not full speed but I can check for alignment etc. No matter how much the preview drags, the rendered output should be fine.

Regards,

Carl