Please specify your question a little bit more precisely.
VMware is a company which sells virtualization technology whereas the Microsoft .NET Framework and ASP.NET respectively are software technologies.
You can of course install Windows Server 200x on a virtual machine and run an IIS on it to host an ASP.NET Website, but because both technologies are fundamentally different, I would not call this a combination.
There are some advantages of running your webserver in a virtual machine:
You can isolate the virtual machine from the rest of your infrastructure, what makes your system safer when being attacked by some hackers or so.
You can make snapshots of virtual machines which saves the current state of the virtual machine. You can then later roll back to any snapshot you want.
Best Regards
Oliver Hanappi