Yes, Win 8 has some funny ideas about where to put files at times. As for your project, I think some more information about what you want to do would be useful.

SVG format is only for 2D drawings (flat plans and cutouts), for your model you need .obj format (or kmz/dae or some of the other 3d formats if you import from elsewhere).

I still don't understand your sunroof issue, but there is a round window included (in later SH3D versions) that can be put in a wall and exported/imported/rotated (selection of window and wall) to form a roof with a round window (skylight). If you want a round skylight on a flat roof(?), there is one already in this file which you can copy. See SF 3D 308.

ok