Really need someones help

Hello,


so i got this trojan called antimalware doctor and i've had this problem before with a different fake malware detector so i really thought i knew how to fix the problem. I thought i got rid of it by using malwarebytes and i really thought got rid of the problem cuz that trojan is gone. The problem im having now is that i tried to do a system restore and for some reason an error pops up that it can't do a system restore on my external hard drive cuz it was disconnected. i look over and it is connected cuz the light on it is working but it's not showing up anywhere on my computer. it's not my usb ports cuz i have my keyboard and mouse hooked up to it and my ipod. i dont know what the problem is but i dont know there is still something on my computer because malwarebytes is running and it keeps saying its blocking malicious sites and my explorer isnt even running. i also run malwarebytes scan and it quarantines the problems but they come back immediately. i would get rid of them manually but i have no idea where to begin looking and i also dont know if its in my internal hard drive or my external or both. i really need help i dont want have to buy a new hard drive or even reformat but i will if i have to.