I need to use Gromacs software, but tool icon is inactive and can’t be changed!
Thank you so much.
If I understand your question correctly, you are tying to start GROMACS by double clicking on a tool icon on your desktop.
GROMACS does not provide a graphical user interface that loads upon double clicking an icon, as you might be used to from other applications like Word. Instead, it may only be controlled via commands that are entered in a special terminal application. Under Windows, this would be WIN+R, then entering cmd. To take further steps from there, a good idea might be to follow some of the tutorials that are provided for GROMACS here: http://www.mdtutorials.com/gmx/lysozyme/01_pdb2gmx.html