Problem copying the file from DVD to harddisk

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I just used nero to burn some mpg file to my dvd-r. Then when i try to copy those mpg back to my harddisk, i failed to do that. It said cyclical redundancy check.... But I can play the video from the dvd perfectly fine.... Then i try it on another pc, i can copy it to the harddisk. Do you know why it happens to my pc!?!? Or is there any setting to stop that check so that i can copy it to my harddisk?? thanks.
P.S. I saw one topic talking about it, say it is the physical problem of the dvd. I saw there is a very slow scratch on the surface, but that is only at the top part, not on the bottom.

[setarip]

Try cleaning your burned DVD...

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How to clean?? I tried to use some tissue to clean already......
But it only has problem when i try to copy it to my harddisk.... other computer and playing it is no problem..

[setarip]

You should simply use Windows, NOT NERO, to copy the files back to your hard drive (Open one window for your hard drive and another for the drive containing the burned DVD. "Drag and drop" the files/folders from the burned DVD into the hard drive's window)...

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Yes.. I used Windows to copy it...
Just now i tried to clean it again. And try it, this time, it works!! but it seems it sometimes works, sometimes not. Just like see my luck. If I am lucky, I can copy it. If not, i cant!
I also have one more problem. I have a dvd-rw. At the first time i tried, it doesnt works, i cant load it. Then i update my dvd-r/rw driver. And then it can read that dvd-rw. But now, when i put the dvd-rw inside, and double click the drive, it says:
"Windows cannot read from this disk. The disk might be corrupted, or it could be using a format that is not compatible with Windows"
Do you know why?? It is because of the dvd-rw problem? So what can i do for that?? thanks