hi smart people,

i'm using WMM for Windows 7.  I use my basic logitech video webcam for surveillance.  my computer is an acer V5-131 series.  my question or questions are 1) why does certain videos runs smoothly and others pulses which makes me want to hang myself.  I download my video from my older computer to a portable hard drive.  I use my 3.0 drive.  I get don't get it.  2) another issue is that sometimes the audio waveform shows and sometimes it doesn't.  it makes it a whole lot easier to view a video know that noise is being produced.  I find watching an 8 hours video at 64x speed pointless if my video pulses which can take an hour, where a smooth running video make just take 4 to 7 minutes.  Can anyone offer any suggestions or help?  I know someone is coming into my room when I'm away.  Or is it just WMM imperfection and I can't do anything?  I'm hoping I can solve it.  Thanks!