I'll just throw this in here now since the coffee just gave me a massive "power surge". You can do a bunch of stuff that can sometimes fix things and never hurts. \
Chkdsk /r is one, doing a massive defrag also. Check to see if the HD isn't more than 75% full of data. Post specs of power supply, check temps using temp sensing software. This forum seems to like Speccy, but there's a bunch of them. You can also sometimes check voltages and temps in BIOS. Make notes and post them here if you do any of this. BIOS data is most reliable.
MSCONFIG will sometimes reveal that there are oddball and usually bad programs installed. If so it's best to uninstall them and not turn them off in MSCONFIG. Also having a secondary logon account can also be bad, since while you are in the primary, software in the secondary account can be "doing things" you can't see. Example mom lets son have his own account, and he gets it completely infected and it's running in the background screwing the pooch for her primary account. Meaning if you have multiple accounts and aren't using them, get rid of them.
One goofy option to try is to boot into "Safe Mode with Networking" and see if internet speed gets GOOD. If so, then some software is degrading internet connection speed when running in Normal Mode.
But again the LAN connection is the real-deal. Not doing that is a real problem, because what if the problem is the wireless functionality of your wireless modem/router? You'd never know until you moved the computer off wireless? Also as I think about it, what if some other computer is connected to the wireless and hogging all of THAT bandwidth? Best way to rule that out as the cause is to just turn OFF the wireless completely , connect your computer to LAN and see what happens. What if someone's Android has P2P filesharing software installed and is hogging bandwidth of your wireless network, downloading porn or music files? What if your neighbor has hacked your wireless network and is trying to hack the Pentagon? You don't want Feds showing up at your door, do you?
So anyways, that's just a few reasons why we need to remove the entirety of the wireless functionality from the table, in order to rule it in or out as the cause of the problems. You can thank Folgers for all of the above.