Over the last couple of days I've noticed a slow down on my main pc and generally with accessing the web. So was it my ISP or my PC.
Many people over the years have asked me this question and how do you know before you call and complain to your ISP or start looking at your PC.
The easiest way is to first eliminate the Internet connection. To do this you can access anyone of many bandwidth checkers. What these utilities generally do is conduct a small file transfer in both directions and measure the time it takes to for the file to transfer. In other cases they simply do a test called a Trace Route and measure the time it takes for servers to respond. In either case, they can give you a sense of your bandwidth speed (does it match what you’re paying for) and how many errors are encountered along the way (causes of slow downs). If all looks good then it's your PC, if you have lots of errors and your bandwidth is off, then it's your ISP.
My favourite tool for testing my connection is MySpeed Bandwidth Test.
In the past, I've caught one ISP who had reduced my bandwith speed to a lower level then what I was paying for. Unfortunately today it’s something with my PC and I now need to spend some time figuring out what. Until then, at least I know my connection is good.