I have AT&T U-Verse DSL. I know DSL is not amazingly fast but the past 3 days i noticed a big difference in speed. I went to speedtest.net and did a test and i got .66 Mbps Down and .64 Mbps Up. When I should be getting at least 2-3 Mbps Down One of my buddies was playing around with my router settings a couple days ago for port forwarding and its been slow ever since. It might be somthing wrong with my router settings of ISP?
I am using a Ethernet. I cant even play HD Videos any more it auto detects my connection to be 240p Quality when watching Youtube Videos!
And Yes it is like this with more than one computer in my house.
The easiest thing to do to fix what he did would be to reset the router and setup your settings over again. Reset by holding down the button in the small hole on the back of the router, that will default everything to the original state.