It is a free scan ONLY, then you have to pay for the program to fix what it reports as errors.
It is widely reported as useless, sharp marketing, constant annoyance in telling you that you have tio buy the product
If it is not shown in add/remove programs, have a look on C Drive Program Files.
Be careful you do not click on the install for the program if it is still in the program, otherwise if it has been partly uninstalled you will re install it.
It is widely reported that the only satisfactory way is to use an installer, such as Revo, but as always care is needed to ensure you are deleting the correct files it may be easier to leave it as is.
Re HD Tune - yes leave it then and uninstall CPUID
Re startup - either just take out the check mark, or use WinPatrol.