I agree with delstar. If you want to write virii (i'm not sure why), you really have to learn assembly. It's probably a good idea to learn it as a programmer anyway. Learning assembly just gives you so much more insight into how software interfaces with hardware, memory, registers etc. Here's some good places to start.

http://burks.brighton.ac.uk/burks/la...smtut/asm1.htm

http://www.comprenica.com/atrevida/atrtut12.html

http://www.cse.cuhk.edu.hk/~csc2420/reference.html