Virtual PC

Our comapany are about to embark upon virtualizing our server environment.

We have both VMware products and and Microsoft and i am am just about to look at SUN’s virtual box.
Microsofts virtual Pc was easy to install and seems pretty fast and user friendly. I have also tried to install VMWare’s ~ESX the 32 mb platform edition. which i am still unable to install.

What i would like to know is if anyone has any advice on virtualising a corporate environment around 20 servers and 300 desktops.

Any advice greatly appreciated software used, platforms used etc and links to downloads if possible.

Any assistance greatly appreciated