Maybe if I have installed linux before on this machine, lets say Xubuntu, can I just use then the existing partitions? And I don't have to do any more partitioning? Xubuntu does all this by itself, and doesn't ask me anything. That would be a great solution for me.
Yes, you can reuse a previously existing Linux partition and a previously installed Linux swap partition. Just direct the VL installer to use the former Xubuntu partition when you get to the step after partitioning (which you can skip). VectorLinux will format the existing partition with whatever Linux file system you choose. You don't have to erase anything first. Of course, everything on that partition will vanish because of being reformatted.
I wouldn't want to have an installer automatically take over a partition without asking me.