If I'm trying to edit relatively simple videos, what is a good non-linear editor available on Windows?

These are the features I'm looking for:

• trimming video clips
• combining two clips (play one after another)
• ability to insert images, video, or audio at arbitrary points on top of an already existing clip
• previewing the video before exporting it (ability to play/pause video to find places to insert things)
• preferably free