To all one man band who only has a computer... well like me.. this is what I use...

First I installed Jeskola buzz from www.buzzmachines.com (free)
then Zero-G's Vocaloid (well I got it free though it's not freeware)
Then goldwave (same thing)

They are both hard to use at first but once you got used to it then you'll be having a professional like cd's