Hello Vy: As of now, , the MPower only records its material in .wav format. So, yes, files, even at the lower bit rates, can get a bit bulky. This means a single class can take up 50 to 60 mb of space. Now, that being said, remember that the MPower can record on any of its internal or attached drives. So, if you were to attach a 20 gb USB hard drive (Be careful of compatibility and power issues), or even a 1 gb SD card, you'd have plenty of room to store your lectures.
The MPower's internal microphone is very sensitive and at the higher recording bit rates, is excellent for recording close in conversations or in a very small classroom where you might be seated close to the front. The only problem is that when using the internal microphone, your note taking can be very loud and if you use voice, it can get really loud. For recording lectures, I'd use an external microphone. There are plenty of them out there at many different price levels. I have a $20 Sony that does the job nicely. hth Jeff
