Thanks! I tried foldersizes and DiskView. Not tried JDiskReport yet. Is it better than those two in having more functions?
Anyway I did a very very bad rookie mistake which is kind of unbelievable to me. I wanted to free space on my windows hard disk and saw a directory in windows called "installer" which kind of seemed like a temporary directory to me, so I deleted it! Big mistake! I was able to use the repair functions of the Office installation but can’t use the repair or remove function of Visual Studio or Norton SystemWorks. So I’m kind of mad right now!