I accidentally dropped a fairly heavy book on my Acer Aspire 7720Z laptop yesterday and since then it's started making this horrible, loud buzzing/crackling kind of noise - it doesn't seem to start immediately when i switch the laptop on, but once it does start it's there all the time. I have no idea what it is but i'm guessing this means i've damaged some internal component. There don't seem any other signs of trouble, everything appears to be working as normal and i haven't had any kind of error messages appear alerting me of a problem. Please help, i'm worried about it now and i have no idea what to do.