If you are going to download stuff at all, ie using p2p such as,
O9 - Extra button: BitComet - {D18A0B52-D63C-4ed0-AFC6-C1E3DC1AF43A} - res://C:\Program Files\BitComet\tools\BitCometBHO_1.1.11.30.dll/206 (file missing)
Get an ANTIVIRUS, You have just proved that you really need it, it wont cost you anything.