The obvious candidates are Virtualbox and Virtual PC.
But I have not been paying attention to VM's the last year, have I missed a good alternative?
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Sign up to join this communityVMWare player is also free to use, and can create virtual machines as well.
What's wrong with VirtualBox? That's still the best free one I've ever used.
I agree. I find VirtualBox has the best feature set of any of the VM solutions out there and its free.
I have yet to see another VM app support the seamless mode feature of VirtualBox which IMO is the one of the coolest VM features out there.
I install custom laptops for our users, many who need access to dual OS'. Since we started using a minimum of 4GB on laptops I've recommended virtualbox whether the host is windows or linux, the guest OS always being the opposite.
I use this myself, and all users I've set this up for have been very happy with the results, which are much better than dual-booting, although with lower performance, which is very seldom necessary anyways.