Internet Lag every few minutes

[Exo]

Ok, I have one really big problem. It all started when I installed windows 7 on my PC.

Before that I had windows XP, and I had no problems. My PC performances: Processor 2.5Ghz Dual Core;

2 GB DDR2 RAM; 512 Graphic Card (ATI Radeon 3650); 160GB HDD; Gygabyte S-series 945gcm-s2l motherboard;

PCI Bus 10/100Mbps Fast Ethernet adapter - DFE-528TX; huawei smartax mt882 modem.

The Problem is that when I am online, every 6-7 minutes a huge Lag comes and I can't do anything. The lag

happens only on internet applications and only when I am using internet. It happens in every game and in browsers,

but its preety hard to see it on browser. So, I play Counter Strike 1.6, WoW, League of Legends, Quake Live and

many other. I have that lag in every game. It happens every 6-7 minuts and it lasts for 10 sec. during that time

I am unable to do anything, couse ping goes to 1000++ and in normal time its arround 20-30.

Ill describe what happens in 3 games:(WoW: During lag, I can move, but I am unable to cast spells, other people can.;

in Counter Strike: I can't move, I cant Hit.. it all freezes and I got some error message on screen;

in League of Legends: I freeze, but I see other ppl.

wallking like nothing happens)... I have reinstalled my system several times (last time few days ago), once even

installed Xp (there was no problem) so its up to my computer and windows 7. I dont have any Viruses ( I use Avast Antivirus)

but I have scanned it with few other... so its not up to virus or antivirus system. I do not use P2P system a lot.. but

I know how to stop it when I am done with a downloading. All my drivers are up to date. Please help me... I like to surf on web, or to play games but I cant

do anything with this problem....