Make sure you have error checked the drive - you must force Windows to reboot to do this - it has to be an offline check. Do this via the prompt chdksk with the switches - or just do it by right clicking the drive and ticking the options (fix file system errors/scan for and attempt recovery of bad sectors). Let that process run before you try to format the drive.
If you are convinced you have a trojan (specifically a trojan) then your next port of call is here: http://www.emsisoft.com/en/software/download/
a-squared is now a free product; however you may as well take the 30 day free trial of a-squared Anti-Malware.
My educated guess is it is not a trojan as a trojan is a specific form of mal-ware for specific uses.
If you are convinced you have a trojan (specifically a trojan) then your next port of call is here: http://www.emsisoft.com/en/software/download/
a-squared is now a free product; however you may as well take the 30 day free trial of a-squared Anti-Malware.
My educated guess is it is not a trojan as a trojan is a specific form of mal-ware for specific uses.