There seems to be 2 issues here, whether or not they are related to causing the problem one would have to troubleshoot with process of elimination,
Have you looked into the Device manager to be sure all the Hardware components are working? there should be no exclamation Mark beside anything, although this doesn't always mean everything is OK, a Hardware component could still need it's driver reinstalled,
You ar not able to get an on line connection:
Have you tried turning off/on the Modem/router and let it reset...
when the computer Boots-up it's tools trey do you see the Monitor Icon load that shows the connection status?
if the computer is setup to have an automatic Internet connection and cannot connect it should prompt you of a connection problem,.....
although I have seen at times where there may be a problem with the Integrated Ethernet port, and I'll troubleshoot by switching off the MO port and install a PCI Ethernet card and has resolve the connection problem, ....... As has been mentioned and as much as we all would like to help there is not a lot of things other than to troubleshoot and exchange Hardware out to try and locate the problem, Advice & suggestions is about all we can do from afar,
and really cannot advice you to spend money on parts that might not be what you need to resolve this issue, I have boxes of hardware and cards that I use to switch out components when troubleshooting problems,
After many years of paying someone else outrageous prices to fix my computers I decided to go into it myself in attempt to save money, Probably costing me more in the long run
But at least I got some experience on how to work on them, along with acquiring many many spare parts
On a 3-4 year old computer it might be time for you to give yourself a 1on1 crash course of dissecting a computer,
It can help to be able to get on line and find your model and read about other people experience of having the same problems with the same model and what they have done to resolve the problem...:thumbsup:
Be sure to unplug the computer, a computer retains about 5 volts of charge in the motherboard even when unplugged, this is to help with powering it on, be sure to press the power button to drain out this charge,
also you need to avoid creating a static charge by using a grounded
anti static wrist band,