p.s. this is going to work, right? i assume if you lauch malicious code within a VMWARE session - is can't escape the VM.
Just reading this makes me think of the guy who asks if it will hurt if he shoots himself in the foot.

Now, the real answer is, "it depends". The payload of the virus dictates the action. If you're talking worms and malware, these guys are going to use networking to spread so get ready to explain to your CEO why there was a mass outbreak within your organization.

FREE SAFETY TIP:

Get an isolated lab environment.
Use samples of worms/viruses/malcode that have a *known* payload. This way you can watch it using a sniffer, etc.

That said, here is a free online library of virus/worm/malware samples:

http://vx.netlux.org/

BE CAREFUL.

<EDIT> Optiq hit POST just before I did. He beat me to the punch on the VX Heaven site.