Which distro did you install? If you installed Ubuntu you should be able to change it by updating two files. Follow these steps:
1) Open a terminal (control-option T)
2) sudo gedit /etc/hostname (change hostname to parallels, and save)
3) sudo gedit /etc/hosts (change hostname associated with 127.0.1.1 to parallels, and save)
4) sudo reboot now (restart your system)