Virus re-installs itself after I restart computer. How do I make sure it doesn't come back?

I have swept my system again, it caught the trojan virus, and I ran another program that didn't pick it up, since the other software program quarantined. This is good, but how do I make sure that this virus doesn't re-install itself when I restart my computer, because that's what happens. The programs I am using is Spysweeper (the one that says it quarantined but when I restart the trojan re-installs themself on my computer. WTF?) The other program that am using is Trend Micro Antivirus. How can I make sure that it doesn't manifest itself (the virus) again when I restart my computer? I don't know what else to do, I don't even know what's legit anymore, since this is how I got nailed in the first place. Any advice? The program works, but somehow the virus keeps coming back.

Virus re-installs itself after I restart computer. How do I make sure it doesn't come back?internet security

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