How do I edit text on a header template?

I have downloaded various website header templates with demo text on them i.e "This is where your company name goes"

If they are designed for photoshop its easy to edit the text to my own. "Find and Replace Text"

But on other header templates I can't do it this way. Is there another way that I can do it?

Thanks

If the headers are a .jpg, then you are going to have a harder time editing it out. If they are are .psd, then it is no problem and you can just change it easily. JPG's are 1 layer, while PSD's are multiple layers with a specific text layer for you to edit.