Cannot open files made by other people - I am a WINDOWS 8 user

Hi,

I am new to grasshopper.

I have Windows 8 and I had Rhino 4 installed with the correct grasshopper.

I can only open files which 'I' create in grasshopper & then once I have finished I can re-open them and it works fine....

However, when opening a file which has been copied onto my laptop from somebody else computer, I cannot open that file (.gh) and I get the following response:

I get the following message when I click yes:

I installed Rhino 5 with the correct grasshopper and this did not make a difference.

I have now system restored my laptop to an earlier date (in case I clicked an incorrect button) but yet again this made no difference to opening that .gh file.

I now only have rhino 4 with the correct grasshopper to go with it.

Please help

B