That's effectively what Sandboxie is, and although it does what it says, it increases the demands placed on your system to run a given process. It really isn't that much different from installing VMware for Windows, creating a Windows Virtual Machine, and running your applications within the VM install of Windows rather than in the host install of Windows. In other words, that works fine unless you're running up against your machine's capabilities for processor speed or data throughput, in which case that extra added layer of interpretation will mean you hit your limit earlier than you might otherwise. If you're doing stuff that's not processor intensive, or not writing a huge stream of data to the hard drive very quickly, it's fine. If you're trying to work on many tracks of 24 bit audio with a bunch of plugins and soft synths and samplers, you'll be constrained at a lower threshold by using Sandboxie, VMware, Parallels or that sort of thing.