How will i get the data of the old virtual machines? I thought to use an imaging software like acronis, but is there a better way
Instead of re-creating all the VM's back I would sugges to backup your VM's using ghettoVCB or Trilead VM explorer (Assuming your are uisng Free ESXi)
Or
Export the VM's as OVF file on a external disk and once you have done the fresh install and deploy the VM's back