YM status changing itself

hi,
my ym has a virus…. it changes its status itself… and send messages with links to everyone on my friend list… i removed this virus once… reinstalled my ym but it reappears…. also my task manger and registry editors were disabled…. i installed a third party registry editor to enable registry editing but when every i open task manger and registry editor(original windows not third party) it just opens and closes in a flash…. please help…