rubbish as it is, sound recorder.
i think that's the only really good thing about it: it supports mixing -- and very easy as well.
so, you open a wav file, wait for the part you want to mix another file, when that part comes you stop it, (right at the part, remember!), and then you go to edit and mix with file. then you choose the file you want to mix. then you play it back. do not save it unless you get it correct. if you do something wrong and save it you will not be able to get it back the wayit was. however, if you do revert it will remove (all) changes since you last saved. if you save a file, this option will not be available unless you make another change when you open it again, but even then it will only undo the changes you made before the time you opened it when it was saved.
that's a disadvantage. sound recorder is quite powerfull and simple to use when it is mixing, though.
hope this helps