I want to practice working with guest operating systems using VMWare. So I will install 2 Win XP VMs and 2 Windows Server 2003 VMs.

If I had a Core 2 Duo computer with 2 GB RAM and reason hard disk space, would that crash the host operating system (main computer).

You will be able to run VM at a time with no problem, 2 at a push but no more.

It all depends on what loading each of the guests will put on the Host, whether you will be able to run two

I have a laptop with a similar spec.

This is what I am hoping to do:
Core 2 Duo laptop with 3GB RAM, 120-250GB HD

VM 1 - Windows Server 2003 with 512MB RAM, 4-8GB HD
VM 2 - Windows Server 2003 with 512MB RAM, 4-8GB HD
VM 3 - Windows XP with 256MB RAM, 4-8HD
VM 4 - Windows XP with 256MB RAM, 4-8HD

Something like that I was proposing.

google is your frinded:

VMware Test Lab Setup Instructions

Setting Up A Virtual Pc "complex" Network - Forums

its possible.. as all depends on how you set up each host on its memory and process uses