which is the most effected virus till now?

a keylogger can wreck havoc to a PC than a virus, it can turn ur PC into a password stealing machine! anyways my yahoo account was once robbed but i could still login but i came to know of it only when i had to enter a chatroom in yahoo messenger using my other ID and find my original ID there. thereafter i came to know that my account has been hacked and i changed my password immediately.

I suppose you mean the real virusses. Not pc-virusses. I think the fluu in europe in the beginning of the 1900's. I guess it was a type called the spanish fluu. It killed more then 10 milion people. When epidemiologists refer to a worldwide breakout of a virus. For example the bird-flu, they take the spanish fluu as an example.

i have some problem yesterday with a keylogger someone has steal my e-gold password and my email password and steal me 20$ now i have clean my pc and changed all the passwords