Problem with Ping in online games

Hello everyone!
A week ago i have installed Windows 7 professional, and i have a little problem.
The download speed is ok and the speedtest also look fine, like on XP, but when i installed Steam(CS) and War3(DoTA) i have jumping ping. For example i play 5 sec on ping 40-50 and then for 5 sec 150 and again 5 sec 40-50 and again.
It's impossible to play like this. Maybe someone know how to help me? I've searched for answer but nothing seems to help me. Please help me, i don't want to back to Xp. And sorry for my english.

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