[MovedGoalPosts]

One assumes all your PCs are on the same workgroup name. I also assume the folders you want to share, and files within those, now allow the right access - if in doubt for the purposes of this give "everyone" access. You can always try and set specific accounts later.

Now on the Win 7 PC:
control panel > Network & Internet > Network & Sharing Center
Make sure your network type is "Home" or "Work"
Left hand side: Click Change Advanced Sharing Settings
Set "password protected sharing" to OFF