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If you burn a disc while bitcomet is running, and if you save files in the same HDD where you save data to be burned on a DVD, this is certainly a cause of problems.
In fact, when more than a software access to hard disk and the HDD is not enough fast to satisfy all requests, this can cause slowing during the burn, and this can hugely increase the amount of errors on the burned media.
Try to disable any unnecessary software when you burn.
There is a very simple way to see if something wrong happen during the burning process. Can you run the “Write disc Test” with cd-dvd speed?
Create an ISO file with DVD Shrink and save it on hard disk. Then tun cd-dvd speed, and select the “Create disc” tab. Then select both the “burn image” (and also “simulate” if you don’t want waste a disc) options, select a burning speed, and finally press the start button.
At the end, save the screen pressing the little button with a floppy disc near the start button and save the image (as PNG possibly). Finally, post the picture here
Try the same test both with bitcomet running and with any unnecessary software stopped, so we can see if this makes difference
You can find more information about booktype here