I have always been very fond of 3721 and tried my best not to provoke it. But it's hard to guard against... This time I fell for it...

GF wants to play a game, download it, and install it. There was no prompt for what to install...
Open IE and see, it's Yahoo again! One search toolbar, and then there are 3721 toolbars, Internet assistants, Internet real names and a lot of things.
I still feel honest when I search. If I don't like it, I just click Uninstall and it's okay. Clean and clean...
But 3721 is really a hooligan and won't leave even if he is beaten to death. There was no choice but to search for solutions everywhere.

I don't know if Microsoft is involved with 3721 or if it really can't see 3721 anymore, but the anti-spyware software Microsoft AntiSpyware has officially listed 3721 as a rogue software. After downloading, installing and using it, it is the cleanest tool currently available to completely delete 3721.

1) Uninstall 3721.
2) Download Microsoft AntiSpyware, the interface is in English. After installation, follow the prompts to upgrade the latest database and execute SCAN. The scanning time is long. Be patient. Later, you find more than 100 items of 3721, CNS, which are much more than those found by some 3721 special removal tools. Many of them are hidden. Select REMOVE to clear the items of 3721, CNS, and then follow the prompts to restart the machine.
3) Run Microsoft Anti-Spyware again. The scanning time was shorter than the first time. Later, multiple 3721, CNS items were found, but the number was much less than the first time. Select REMOVE, clear the 3721, CNS items, and restart the machine.
4) Run Microsoft Anti-Spyware again and you will find that there is no 3721, CNS*. Completely eliminate 3721.

Download address of Microsoft Anti-Spyware Software [English version]: download.microsoft.com/download/8/1/5/815d2d60-49b5-44dc-ae35-fca2f2c6f0cc/MicrosoftAntiSpywareInstall.exe