Hey, I'm a n00b here.

A friend of mine has a marshall head, and he happened to use the wrong power cord to plug into the head.

The head now does not turn on.

Could this be a result of using the wrong power cable?

BTW, the cable fit into the head port.

Any help would be appreciated. Cheers guys.
Using a different power cord shouldn't have caused any damage unless you are not in the USA and had to use a power convertor. You could have a blown fuse if you forced a wrongly configured connector over the prongs. Check your fuse.