3) I once did the same copy/paste, although it took about 28 mins from hard drive to hard drive, both set on UDMA5
4) 8x media should burn at 8x, but it depends on your burner and firmware and some on your media. For example, I have a px716a and I used Media Quality check on one Ritek Ridata 8x DVD-R and it only passed at 6x, so I burned it 6x. The next one I tried passed at 8x. :eek: If your firmware doesn't support certain media being burned, it's not a guarantee it will burn at the rated speed; as Bob said, if the media is cheap like Princo or some other brand that is known to be bad...
Your Plextor px-716a should be autodetected by Windows XP and set at UDMA4. However, check this screen to be sure what your setting is
If the device where your Plextor is (mine in that screen is the first one, at the top) says "PIO mode," then change it the DMA like it says there--you should be able to select it.