Somebody help: COD 4 Lag?

Only recently has this promblem started, where I start playing online and everthing is going well, when suddenly after about five to ten minutes I suddenly get mive lag and my ping skyrockets from about 100 to 500-600. I never had this problem before and this only started the other day, but it makes it extremely difficult to play. I know the computer can handle it and my internet provider is the same, I don't lose connection, but it just sucks. Sometimes after a few minutes the lag goes away , but most of the time it doesn't. Anybody got any help that DOESN"T require taking apart the computer.