Like Dowly says, Windows Movie Maker is okay as long as you use the effects with caution, most of which are not what you'd call 'subtle', if nothing else it's great for compressing FRAPS files, which are always huge.
This IL2 movie was done with FRAPS and WMM:
Even though I have Adobe Premiere and Adobe After Effects, which both blow it out of the water in terms of capability, I still often use WMM for its simplicity, which is certainly one of its virtues.
Chock