My CS tower is making a faint noise that comes and goes about every minute or so. Sounds like some type of case vibration or maybe a hard drive. In my words it sounds like a faint humming noise that winds up and winds down every so often. It really hasn't been a problem because I mainly record midi instruments but if tracking vocals in a quiet room it is certainly noticable. I thought about taking the cover off too see if I can isolate a vibration but don't want to void my warranty. The unit is about a year old but has done this for a long time - probably since I got it but never noticed it until a while back. Any suggestions?