what do you mean by " I have AVG dowenloaded and am wondering if that is too big for the laptop?" because that makes no sense at all...
Horrible sound, hmm, if it's coming from cd rom then nothing special, it's the drive checking if there's a CD in there and if it's a bootable one. If you wish to disable that, go into BIOS and rearrange the boot sequence.
if it's a floopy drive then yes, those things make noise even when empty
it could also be the fans when they are starting to spin if you are having misalignment issues (pretty common in laptop fans)
any other sound, I don't know, could be something horrible and evil happening, like, hmm, black rabbits making babies or something..