Win7 Speech Recognition is primarily for voice commands to the PC.
But, apparently it can be used for dictation.
It doesn't look like you will be able to just play your father's recordings to get the text.
There is a learning period where the app learns the person's voice and speaking patterns.
Then, you'll have to add punctuation [period, stop, comma, etc] by speaking the punctuation where it is needed.
And finally, there is little doubt that it will take a lot of editing to get everything right.
Even Dragon Naturally Speaking requires a learning period.
I don't think the Windows Speech Recognition will work as well as Dragon does.
I think you are asking for more than normal run of the mill reasonably priced to free software can do.