Complex sentence: It must be plugged into a high-power USB power adapter, such as the HP TouchPad power adapter or a newer high-current USB adapter, because HP clearly shows a warning in the user manual to not plug it into a laptop.
Split into simpler sentences: It must be plugged into a high-power USB power adapter, such as the HP TouchPad power adapter or a newer high-current USB adapter. HP shows a warning in the user manual to not plug it into a laptop.