Don't use Parallels. Use VMWare Fusion. Any guest OS (those you list...except "Win 93" and "Win 96" lol) will work in Parallels or VMWare Fusion. The only difference is you won't have to continually pay for the software with VMWare, like you do with Parallels. In terms of running multiple VMs simultaneously, if that's what you're asking, that mainly a function of your host machine's HW and how you have your hypervisor configured.