Thanks for the suggestions, everyone. I have managed to solve this using eset antivirus software, and it seems to have wiped out the Malware/Trojan. Everything is good now.
Can these really be installed from jpeg or other non exe file?
I don't think so. Most of the Malwares/Trojans come from .exe files. The one that was infected was an .exe file that I don't know where it came from.