Explorer,msn messenger,yahoo messenger are not working
 

HELP!HELP!HELP!!!!!!!!!!!! Don't know where to start! my explorer is not woking...i downloaded a ninja surfing... since then my i cant use msn messenger,yahoo n explorer is not working. I've tried to down load macafee n other software to scan for viruses or spyware.My pc is so bad that it doesn't allow any anti virus software to be down loaded. WHAT CAN I DO????? Am all confuse..PLEASE HELP!