How can I tell that a virus is in my system before it becomes serious and starts making the computer to mulfuction?How do I differentiate virus files from other program files and windows files.is there a program apart from an anti virus that can be used to detect virus files or can detect recently installed programs so that you can delete the virus manually?secondly,how can I remove a boot sector virus manually?how can I search for any virus inclusive of a trojan manually and remove it without any antivirus.how can I access a completely infected computer and delete the viruses manually?

Try IOBot Malware Fighter - it's free and does a scan on all incoming traffic into your computer and catches stuff even my Norton does not.