I did have a copy of Sound2Midi, but I didn't find it very useful. It just about worked from a whistle or other instrument with a fairly clear waveform and fixed note registration, but was virtually useless for my voice, it was slightly better for a clear female voice (less overtones). The program was not capable of working out a time signature and as far as I remember didn't have any metronome feature which it would really need to be able to perform correct quantization.

I can read music, but I find it more difficult writing it. If you do have a simple score-writing program, it is sometimes easiest to put the notes in and move them around until you get the right pitch. Start off by working out the basic time signature - this will usually be 4/4 for common/march time or 3/4 waltz time (6/8 time is only a more convenient way of notating a fast waltz time). If you really can't distinguish a time signature, try marching around while you're singing it - if you can't manage to - it's probably waltz time so try waltzing to it. You should be able to work out the start of each bar by singing the tune and working out where the beat is - marching or waltzing to the tune can help. You can then mark these off on the words and start tryng to work out the times values of notes - rhythms tend to repeat, so often when you work out one line others will be similiar.

If you play the guitar, you should be able to find the tonic key reasonably easily - just find out which chord seems to be the right one to start on. If not use a piano or other instrument to find the pitch - it's probably easiest to work it out from the last note which is most likely to be the tonic.