adware&trojan downloader was detected by using win defender,but when I remove it and succeded,IT STILL THERE.y

Answer 1

Firstly update and run your anti-virus product. You can also run a free online scan as well as some malware can actually corrupt or disable your resident security products. Here are a few online scans you can run:
Trend - http://housecall.trendmicro.com/
Panda - http://www.pandasoftware.com/products/ActiveScan.htm
Norton - http://security.symantec.com/sscv6/default.asp?langid=ie&venid=sym

Second download, update and run scans using the following products:
SuperAntispyware
http://superantispyware.com/
Spybot S&D (free version requires manual updating)
http://www.safer-networking.org/en/download/
AVG AntiSpyware
http://free.grisoft.com/doc/20/lng/us/tpl/v5
Adaware from Lavasoft (free version requires automatic updating)
http://www.lavasoftusa.com/products/ad-aware_se_personal.php

(These programs can be run in Safe Mode after downloading and updating)

Third, after cleaning your system, disable System Restore, reboot and re-enable System Restore when you log back on. This will clear the malware that may still be lurking in System Restore, which could be reinstalled should you need to rollback at some point. Additionally, a reboot may be required to complete the malware removal process.

Lastly, you may also want to install the following tool. It is free and requires you to check for and enable updates manually once a week or so. It uses no system resources.
SpywareBlaster (inoculates, not a spyware removal tool)
http://www.javacoolsoftware.com/spywareblaster.html
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If you cannot get it removed after the above, you may want to join a tech group that specializes in providing manual instructions on malware eradication.

Free technical help forums

AumHa Forums
http://aumha.net/index.php
Bleeping Computers
http://www.bleepingcomputer.com/forums/
Spybot S&D Forums
http://forums.spybot.info/
Lavasoft Forums
http://www.lavasoftsupport.com/
Spyware Info Forums
http://forums.spywareinfo.com/index.php?showtopic=79038
GeekstoGo
http://www.geekstogo.com/forum/forums.html

Answer 2

MML. is right on this matter as well go into your settings and delete it from there as well if you dont it is still in your system do that first then run a relibable scan on yor computer it can isolate it . in my opion?