Install GTA 5 on the second hard drive? PC

Hello, here are some clarifications for the curious

If your hard drive on which Windows is installed is slow, it’s better to install the game on another hard drive, as this will improve loading times, not the fluidity of the game (that's mainly taken care of by the GPU - graphics card - and the CPU - processor - with a bit of help from the RAM - memory). Unless your hard drive is too worn out or infected, that could also improve fluidity.
So for all of this to be useful, the other hard drive needs to be of equivalent speed or faster compared to the one containing Windows.

If you have an SSD, you should install the game on it, even if it contains Windows. This will significantly speed up loading times, and the difference in speed with a regular hard drive is such that now loading times will mainly depend on the CPU.
If you have a second SSD, you might as well install the game on the one other than the one that contains Windows, so you wear both out at the same time (and therefore more slowly).

Note that in all cases, installing the game on another partition of the same hard drive is practically useless in terms of performance.

Let me tell you that if you have a crappy processor and a crappy hard drive, it's better to change both at the same time, as in most cases the overall execution speed depends on each other. If you buy an i7 CPU, you might as well buy an SSD with it.
You could end up lagging like crazy with an i7 because your old hard drive won't be able to transfer data to the CPU, and as a result, the latter is used at 10% while the hard drive is at 100%. The opposite problem is also possible, for example, with an SSD and an old processor.