we need a little more info. what type of file are you trying to open? what software is opening.

any web site, watch a video or listen to a song on any web site.

still working on it. need more.. feed me :)
what type of connection? modem, dsl, cable?
browser used?
It sounds like either a sound or registry problem. in the mean time you could try to remove and reinstall your sound card and maybe update the drivers, depending on connection you could also remove and reinstall the network card and modem. This would give us a starting point to work with.

phone line tells me you are using a modem, browser is what you use for the internet. internet explorer is the usual. low sound in the speakers tells me their may be a problem with the modem or sound card. I would go to control device manager and remove and reinstall the modem and sound card.