downloader.winshow.an message..please help

hey everyone, ive apparently picked up a trojan and everytime i open explorer i get redirected to res://jrybu.dll/index.html whether i change my homepage or not then i get a message that says ive picked up a trojan downloader.winshow.an. i have no idea what to do but i downloaded hijackthis and have noticed i shouldn't touch it unless i get help from experts which i am not! so please someone help me get rid of this and just tell me what to do.
thanks.