Wow someone still uses a modem,

When you connect a modem to another modem or your internet provider using a modem. What occurs is your modem dials, then it attempts to connect with the other system by emmitting a series of tones. This is called handshaking, during this process the two modems exchange tones and negotiate a agreeable speed at which to communicate at. After all of this handshaking and negotiation is completed you computer is usable again and you are connected (if all goes well) and things are quiet.

Hope this explains things for you.

Well you didn’t actually mention all the specs. and programs installed in your PC so i can’t really help you but heres the catch try remembering the last time you did, why your PC turned liked that. Did I install something? Is it like this before? and so on. But to really satisfy your need try consulting a highly trained technician.