Internet Spikes

I've been getting a lot of internet spikes recently and is affecting my calls on Skype and my gaming. It's so bad that I can't have a decent game without freezing for about 20 times each round and that my friend can't understand what i'm saying. I'm using wireless by the way. I know that there is already a lot of threads about internet spikes but none of them seems to be working for me. I have scanned my PC using Avast! and Spybot: Search and Destroy, i have gotten rid off anything that they found. I've solved this before by switching to a faster adapter. That solved it and lasted a very long time, just recently it has started again. Also, I have connected it straight to the router before and did solve it (this is before, I haven't tried it this time around). Unfortunately, the PC and router have to be in different rooms. Does anybody know a solution to this? Thanks.

Please consider your suggested experiment with connecting via Ethernet cable.
If the problem disappears, then you would know to focus your attention upon the radio broadcast from your Router.

If the above makes no improvement, then most likely you have other background applications and processes intermittently hogging your bandwidth.

Install a copy of CodeStuff Starters, which will help you follow the applications and processes that you have running actively.
or
Keep an eye on your Task Manager

If you still find nothing from the above, and your Router is correctly configured (it probably is, since you "sometimes" get good through-put) then you may benefit from a trip over to our Infections Removal Forum to see if you have any hidden bad-guys at work.