In my experience with electronics, a rapidly flashing power LED could indicate a few things, but it often points to either a power supply issue or a hardware malfunction like the HDD failure you mentioned. I had a similar issue with a different device, and it turned out to be the power supply not delivering the correct voltage. It's worth checking the power adapter with a multimeter if you have one, or trying a replacement if it's compatible. If the problem persists, it might indeed be the HDD.

When dealing with such technical issues, I also look for guidance online, especially when it comes to understanding the specifics of LED signals and troubleshooting hardware. You can also read here insightful information on LED technology and its applications, which might be useful for someone interested in the technical side of how LEDs are used in various devices.