Yes
I've installed all parts of an Enterprise Server, (Application Server, Database Server), Deployment Server, Terminal Server and Web Server on a single workstation with VMWare (
http://www.vmware.com).
I would use the far more mature VMWare, since it not only has many flavours (including ESX and GSX Servers, as well as a virtual SMP version) - but it also allows the user to install any type of virtual i386 operating system on the host machine - including NT 4.0, Linux and FreeBSD. This is far better than the Microsoft Virtual PC which is restricted to supported Microsoft OS's. I believe that Microsoft license much of the technology from VMWare, which just got purchased by EMC.
There are some limitations however. The lowest-end license, VMWare Workstation, will only address a total of 1Gb across all machines. (ESX and GSX server goes beyond this, but at a substantial price difference). However, the CPU rate is approximately 99% of the host CPU, which is extremely efficient.
Naturally, the way around the memory limitation is to create a Deployment Server with 128Mb, a Terminal Server with 128Mb, give the Enterprise Server 256Mb and if need be, give 512Mb to the web server. If you do not plan to use the webserver, then double each of the previous servers.
Usually, however, I place the Database on the native OS, together with the application server - which leaves the 1Gb for Terminal Server/Deployment Server/Web Server.
Download the trial version (it works for 30 days) - its extremely easy to implement.
Lastly, of course, you need a TON of hard disk space available, since each Virtual Machine will reserve the drive space on the host machine.
A full package takes about 11 hours on my all-in-one machine, which is an AMD 2.4Gz with 1.5Gb RAM, and relatively slow drives.