Is my data on the laptop all gone when I change the hard drive?

I'm doing a distance learning course and would like to take online exams. However, a person ("Proctor") has to access my PC to release the exam. Theoretically, he can access everything on my PC. Could I just replace the hard drive beforehand to avoid this? And is it worth it? Or should I buy a simple, cheap netbook on which I take the exams?

If you no longer need the data on the hard drive, you can do that.

Yes, I still need it. I would replace the hard drive for the test and then put the old one back in.

Usually there's only one HDD in the laptop, if you take it out, the operating system is gone. Then you have to install the operating system on the new HDD.

Everything stays the same on the old DD as it was.