I have the same problem. The only solution that I can think of is to record the computer sound with Hypercam and use a program such as Audacity to record your commentary, then sync up the commentary with the video manually.
Whats your computer specs? I can run FRAPS at 60 Frames but I have a good computer. So I would just say if HyperCam is you only option do what someone already said use Audicty and sync the video and commentary together. Good luck.