I fixed it myself. I will write how I did it tomorrow, in case someone is interested or have additional feedback.

Ok. So including the asp files in the visual studio project, it didnt work. I tried another solution, I made a virtual directory in the IIS and pointed to the folder with the asp files with the images and css. It didnt work for some reason. So I tried to, under the asp.net tab, to set the asp version to version 1, then all crazy broke loose: the site still didnt work and on top of it the "parent site" didnt work either. Fortunatly this was on a development server.

Well it seams that you cant have a site run on asp 2 and then have a virtual directory under it running on asp 1, without a seperate application pool for the virtual directory. A deleted the virtual directory and restartaded the IIS a couple of times, the ordinary site now worked.

Its a bit of a mystery why the virtual directory didnt work with the asp set to asp 2, however. A friend told me that on newer windows server OS Microsoft dont include support for old asp, so maybe it was that.

The solution was, however, to make an virtual directory on another site, both running asp 1, on an old server, and it worked fine.