|Noodle jokes aside, it could be any number of things, most often the connection to your ISP is flaky. Do the usual things first: Scan, defrag your hard drive, upgrade your drivers, and install all Windows updates. Check your connections starting with the PC and working your way to the wall to make sure the plugs are clean, not rusty or corroded, and inserted firmly into the devices. (I've seen this clear up after a bit of green crude was found on the phone cable connector pins.)|
If you're using dialup or DSL pick up a phone receiver and listen for crackling noises, echos, or other odd noises on the line. Line noise can really screw up your connection; have your phone company check the line for noise.
Now go here: http://cable-dsl.home.att.net/ and follow the guide for tuning your connection. Installing Navas's registry tweaks can really improve your throughput.
Finally, your ISP may be at fault. If you have a cruddy connection you can only improve it so far. Do all of the above and see if your problem clears up. if not, consider another ISP if you can't get them interested in checking their hardware