XP Possible Trojan / Commendeared My System / Seems To Be Bypassed But Not Removed

this is the message i get when running a "heavy duty" trojan remover: called trojanhunter 4.the entry in your system registry that specifies how to open an executeable file is not set to %*%1, as it should be, but instead the value is ". some trojans alter this key to make themselves autostart(which ive been experincing everytime i open program) Do you want to restore the default value for this key(recommended).when i open any program a screen comes up sayng: to protect your system from bad things: have this box clicked: when doing that a trojan runs on my system: i've lkearned not to trust that box: and run as if i didnt want protection::