Hi Arbabi!
Can you expound your question? I can't clearly understand what you mean.
Anyway, if you mean turning off the display of links in the Bar Chart: Press F3.
If you mean turning off the the relationship links in PERT view: From the menu, click: Format, Relationships. And then remove the checks for Driving and Non-Driving relationships.
If you want to remove existing relationships, check out the Help menu and do a search on Global Change.
Hope this helps.