Trojan Detected! Please HELP!!!

Hello,
I just bought this new HP laptop several months and now its infected with malware Trojan. A full scan on Windows defender shows that trojan is detected in some of the .dll files. I deleted 2 files on which it said trojan was detected. But next time I scanned on Windows Defender, some other .dll file showed up. Also scan on Bell Sympatico's Anti virus service, it shows no virus or spywares.
My laptop is very slow than before, and also internet explorer browsers keep opening and they take me to some random antivirus sites.

Please if you could tell me what to do in getting rid of this Trojan and make my laptop run as normal. I would really appreciate it.

Thanks in advance. Hope to hear from you guys soon.

Rounak