Use VMWare ESXi server, its free and alot better.
You install it on the machine like Proxmox, but you log into it using a client, and you have awsome management tools.
From the box you have a console screen basic setting can be set so you can log on the box.
You can download virtual appliances to load on the the box as a virtual box.
OR
Just install you're own, i just it all the time, its also great to rigrate you physical system to virtual, (to go green ;/ or just for a back up:D)
Seriously check it out i use it all the time.
Work and at home.
Its based on a Linux kernel, its really easy to install, the only drawback is the hardware support,
Mainly produced for corporate servers. so IBM HP ect are supported.
there is desktops that can run it.
Check this link and you can see if you're hardware is supported of not.
http://www.vm-help.com/esx40i/esx40_whitebox_HCL.php
...Sluggerzz