uh, I found the problem!!
. Just for the record, it was this: In properties Advanced/Compile As , I has "compile as C" ,
. I was testing something in the morning and I guess was copied to all projects somehow (still dont know why all other projects had it also? even though I started new projects). So that should be "compile as C++". Its strange that even after re-installing it was still there , C compilation. Maybe it stayed in the registry.
If a moderator can delete this post, maybe best to delete as it was not a SFML issue. or move it.