So I got the error: "The process cannot access the file because it is being used by another process." This has got to be one of the most hated errors in Visual Studio 2005 since it's often so ambiguous! No file was mentioned, just the message above. This was deploying to a Windows Mobile device (well, emulator anyway). I double-checked the file, restarted Visual Studio, no dice. Finally I got the bright idea to simulate a soft reset on the device itself. The was actually on the device itself, not on the dev machine. This makes sense. I had left a process running on there, so new files couldn't be moved. Even restarting the device emulator didn't help since, like a real device, turning it on or off doesn't actually reset anything. A soft reset did the trick though. Be careful when saving state on the emulator, and reset as necessary!