Cannot open hammer editor

[NathanJD]

It gives me this error message every time I try to open it:
%1 is not a valid Win32 application.

I have no idea whats causing it

 

[giant384]

try reinstalling it. also if its your first time opening it then you will need to open hl2 beforehand after you install.

 

[NathanJD]

I just tried both it still gives the same error message. This is frustrating.

 

[Beerdude26]

Check the Steam forums for a related or similar thread aswell, we don't get many SDK problems here