images in posts cannot be deleted

Hey,

i posted this topic also in the localhost section, but im not sure if it fits better here, im new to wordpress and not sure to what category my problem is related more:

its a longer story to get to the core of my problem. Im updating a webpage, on the current webspace the necessary updates are not installed for the latest WP install, so i decided to work offline with xampp on it. They old website was a joomla 1.5 and i migrated the data to WP. I all worked fine so far.
Now i have the problem that i have always two times an image in the posts, one embedded in the post the other one as a featured image. I can delete the featured image but i cant delete the other one i mean i can delete it but, in the page (the post preview page of my theme) it is still appearing. I cleared the browser cache but couldnt make it working. Btw. Im using the rover magazine theme.

Thanks in advance

Martin