You can record high-definition video with Nokia N8-00. If you are recording video to the memory card, for the best performance, use fast, high-quality microSD cards from known manufacturers. The recommended microSD card class is 4 (4MB/s = 32Mbit/s) or higher.
If there's any performance issues with the memory card, especially if it has previously been used in other devices, it is recommended to format the memory card. You can do this in Menu > Applications > Office > File mgr.. Long press F: Memory card and select Format.