The red light is likely the HDD activity light.
It is normal for it to blink rapidly when starting an Operating System, and blink occasionally, or frequently when the computer is being used.
If it makes a rattle, it's the hard drive making noise. If the rattle is soft and easy to ignore, it's likely just normal operation noises. Hard drives are mechanical.
If it becomes loud or makes any very unusual noises, then it may be failing.
Here is a reference of failing hard drive noises.