"A good test would be to connect your PC to the router with an Ethernet cable and then attempt a large download. If the download works fine on the cable then you know the problem is local."
--I am uncertain of your suggestion.
I had router connected to PC before, when problem occurred.
I have ordered a splitter to split the modem output to my router and CPU.
You mentioned the signal strength. Can I operate the computer and router simultaneously with acceptable results, or will the signal strength be too low?? Is there any method to amplify the modem output through the ethernet cable?