Rendering is just to provide the best possible playback results, and if you have smooth enough playback, you do not need to do it. It creates files just for playback and takes some time, plus adds files to the HDD. If you DO need to Render for smooth playback, you can then delete those Render files, when done.
As for Background Rendering, this was a recent addition. The concept is that one can have Rendering done, while editing. However, what usually happens is that the resources required to do the Rendering interferes with the process of editing.
It was incorporated into an earlier version of Pinnacle, and I think that almost every user of that program turned it off, at least by the responses in that forum at that time.
In fact, once you update to version 8.01, I believe, Background Rendering is turned off by default. I recommend you keep it off. It's way too intrusive.
But it sure doesn't hurt to render your project manually as you're working on it (by pressing the Enter key). As Hunt says, it doesn't much effect your output -- but it can greatly improve the performance of the program as you're editing it. (It can also alert you to possible rendering problems -- which might otherwise cause problems when you try to output your file.)
The problem with your rendered files needing re-rendered every time you re-open your project has a couple of possible causes (depending on where you're storing your project files). But most people find it is remedied by updating to the latest version of Quicktime on Apple.com.
I've got the same problem about rendering, I must run it every time I open my project, which is quite huge, so it takes hours. I've got the last version of Quicktime, any other solution ? I can't turn the rendering off, otherwise, the image doens't run smoothly and I can't do my cut... Working with AVCHD. 4 GB RAM, Intel Core duo 3.33 Mhz... eveything should be fine but it isn't.
Thanks a lot.
Welcome to the forum.
With a Duo-Core CPU, you will likely never get really good playback. Most feel that a Quad-Core is the minimum, while many feel that only a fast i7 will be adequate for AVCHD source footage.
Now, why you are loosing the link to the Render files is a mystery. Where are your Scratch Disks located?