general - Best practice for multiple servers on single box

I look after a number of websites on a Windows 2003 server. There are both IIS 6.0 and an Apache Tomcat application installed on the box.

In the current financial markets our management want to cram as much as possible on the server to save money. I've now been asked to install a third party application that requires Apache Server. I've done this successfully on our test box but I'm wondering if it's a bad idea to be running 3 servers from the one box.

The server has an Intel Xeon 3.6 Ghz CPU and 4GB of RAM.

Can anyone advise what is considered best practice?

Thanks
twave

Instead of cramming IIS, Tomcat, and Apache httpd on the same server, I would virtualize.

It's free if you use Linux and free virtualization platforms ( available from Xen.org, Citrix, and VMware ).

Personally I don't like running more than one app/environment per server. That is what I consider best practice, I'm sure other opinions exist

Thanks iamroot. Unfortunately we're stuck in a Windows environment and the guys supporting the servers will do little to advise on best practice. They will only install or make changes as requested by the developers.

I can only raise the question and let managers decide.

Cheers twave