Windows can't see my computer

My roomate is trying to access my computer through our wireless network, but my Mac doesn't appear on his network, but I can see him. Does anyone know how to fix this so that he will be able to see me? Do I have to go through and pick specific folders to share for him to see me?

Do you have Windows Sharing turned on in System Preferences > Sharing?

Yes, but now my Mac can't seem to find him...I think it has something to with my computer more than his.