What exactly are you after? Testing out operating systems out of curiosity? Testing a webpage in multiple browsers on multiple platforms to see if it works? If we don't know your goals, any advice will probably be too general to be of any real use.
try VMware as OS-simulator
the best program i've ever worked with for that proposel
I've not seen this before, but it's quite similar to CompTIA A+ Windows Simulator which offers many Control Panel scenarios.
I use QEMU (with the KVM module) for virtualisation. Check it out! It used to be slow but these days the performance is right up there with Virtualbox, etc. imo.
I can see where some people might want to use a web-based preview of an OS like this, but I think it would be much more beneficial to just boot up a VM and view all aspects of the OS first hand. I've done this with multiple server environments, Linux and Windows products.
I use Virtual Box and love it.
Xen is good - I've seen it in action. I've yet to try and install it and have hands on experience with it, But I love VMware - its simply powerful and amazing.
I tried Microsoft virtual server / pc and its not as great.
I'm going to try parallels virtuozzo containers as well.
I agree Sun Virtual Box is good and free.
It is amazing that everyone is very happy to express their opinion but no one actually gave useful response to what the original poster asked for. I personally do not use these, but for those who are interested, these are really cheap way to demo your product, it is easy for Customer Support guys to point a user on the phone to take through things step by step remotely as the customer will only have to open a web page to see this. And of course they can be customized to show anything.
Virtualization is totally different and has its place, but this sort of stuff is useful in certain environments where Virtualized OS is not the option.
VM-ware is the only thing i can think of, but then again your questions isn't too clear O.o
the post opens with: What's the best OS simulator you got?
We had several tests at work running. Vmware needs a special treatment running up installs over
a TCP/IP Network. We found out that it was the bios code emulating a pc.
so i can tell you again: Vmware is it. Because i tell you that VMware is nothing more like a good emulating software for every OS you want from windows.
99,8 Percent are clean inside the code, but the BIOS is a mess. So VMWARE is nothing more in my eyes like a simulator.