Recently I came across a software claiming itself as HDD Diagnostic.
Just as rogueware applications, I found this computer optimizers as threat which seems to be causing many problems.
As seen from the below image Fake Hard Drive Diagnostic pretends to be legitimate software.
However, this software does not improve the performance of your PC rather it make your lives harder and more complicated by giving false warnings.
Although the warnings look realistic, you should never trust them or you will be convinced to pay money and lose them.
Hard Drive Diagnostic gets installed after visiting untrusted websites, it does not guarantee the optimization of the performance of your PC.
It is highly dangerous and can only cause problems.
So stay away!