I have installed the game, but when I try to launch it I get a black screen like it wants to load but then after a second you get a window saying W3 has stopped windows will look for a solution. Can anyone help?

Have you already checked these troubleshooting tips from GOG support?
https://www.gog.com/support/the_witcher_3_wild_hunt_preorder/crash_to_desktop

yes i have.

What firewall are you using? Is it by any chance Comodo? If it is set the firewall to game mode. Then try and run it.

Have you already applied all patches up to 1.05?

Also check this thread for useful tips, if you haven't already:
http://www.gog.com/forum/the_witcher_3_wild_hunt/faq/post1

I'll try that thanks.