Hi

We need more information:

1. Computer specification - processor make/model, graphics card or chipset, RAM,  hard drive configuration, sizes and free space?
    
2. Windows version and is it up to date?
    
3. Is Windows the same version as before you replaced the hard drive?
    
4. Software full name and version number - as found under Help, About . . .
    
5. Format and resolution of the video on the timeline
    
6. A screen shot of the timeline may help.

Also please read this post before replying and add any other information you think may be relevant.

John EB