Originally posted by Prince
I know this might be a bit of a bind, but try moving YOUR computer into the place where HIS computer is supposed to be, if you see improvements then you have got something that is causing problems...
I used to play on my computer and have a light on, but it was a very high power usage and affected my connection (wireless) COMPLETELY, I couldn't get on anything not even Google, so we don't use it anymore.
I also got my dad to switch out all the phones in the house so we use wired phones only and my download speed increased by around 80kb/s...
Microwaves and televisions are also another problem, if you use a wireless remote on your tele it (highly doubt it..) could cause some issues and the microwave will too..
They are physical problems that could come into attack, now for the software side of things:
If you want to clean your computer out very easily, then use 'CCleaner' ONLY. Unless you have paid for a PCTuneup from one of these anti-virus companies, i'd recommend CCleaner as it is fast and effective as 1 button cleans your computer instead of having to configure anything over and over...
Check if you're downloading, try to keep your programs / processes closed unless they are completely neccessary (eg: Antivirus, skype and maybe steam) even though you may think you need some programs open constantly, be strict with what you have running in the background as you will always experience internet speed differences (especially if you keep steam running.. lol).
Hardware:
You're not going to break anything if you pop the hood, so do it. But first, shut down your computer (open this thread on your iphone / PS3 / get a laptop going or something to read this), unplug ALL cables going into the tower, move the tower onto a desk so it's not on carpet / fabric and then press and hold the power button for atleast 10seconds, you should see it turn on and then off and keep the power button held down until you can't hear that little screeching noice coming from the Harddrive / elsewhere in your computer.
Once you've done this, open it up. If you can see areas around the motherboard / GPU / CPU area that are BLACK, then get a little bit of cloth in one hand, put your other hand on the metal part of the case so you're grounded to the case and then see if you can wipe it off, if it doesn't come off then you've got an electrical problem with your computer and you need to go and get it checked fully at the place of purchase (eg: PCWorld / Walmart) because you've got something burned out. Also check all the wiring, I know it's confusing but you simple gotta push (firm, but not rough) each cable in with no excessive force to see if any are slightly loose (also a long shot, but worth testing), finally check your WIRELESS card for blackspots / meltspots or if you have an external wireless adapter then remove it, and install another one to see if that solves the problem
I've gone through quite a lot there, I hope I have helped you out mate.