Greg Charles wrote:It's not a simulator. It's an implementation of Unix-like commands for Windows.
I think what OP means by "simulator" is "something lighter than the full OS". Cygwin would fit the bill.
Our Linux/Unix FAQ has many other options. For example, most Linux distributions have a "Live CD" which you can boot up without changing your installed OS. One can also install Linux to a flash drive or dual boot with Windows.
There's also some links in our FAQ about how to get started learning.
VmWare is essentially a software PC. One creates a "virtual disk", actually one big file on your hard drive, and installs an OS to that "drive". As far as the secondary OS is concerned, it's running on its own PC. When you get bored of the secondary OS, you just delete the 8 or so files and it's gone. My employer uses VmWare to do QA against various operating systems. We don't have to keep a lot of old hardware around for testing, just one server with lots of virtual machines.
VmWare Player is free, but it cannot create new VM's. You can either download them or create them online VirtualBox is a free open-source equivalent, but I haven't used it.