As has been documented elsewhere, XBMC's scrapers and library work best when full access to video and audio files is provided to them via an SMB share. However, MS is making it more and more difficult to share using SMB in Windows. You have to turn off Homegroup and do all sorts of other messy things. The following is a guide to quickly and easily turn SMB sharing on in Windows 7.
As a initial step, you should be connected to your network. I, personally, am connected using a LAN cable and have been provided an IP address by my router using DHCP. If you prefer to use Static IP, there should be no real problem. If you can see the internet, you should be connected enough to the router for our purposes. Also, when you are first connecting your Windows 7 computer to your network, it will ask if you are connecting to Home, Work, or a Public network. This guide presumes that you selected Home. The same steps SHOULD work if you selected Work. They will almost certainly not work if you selected Public. Also, sometimes you will be asked to be certain if you want to do something or you will be asked to go up a level in clearance to do something. This guide presumes that you agree to all of that.
2 The Process
Step one: Click the "Network Internet Access" icon at the bottom right of your screen, next to your clock, speaker icon, and possibly power icon. Click open the "Network and Sharing Center."
Step two: Locate and click "Choose homegroup and sharing options." You are now on the "Change Homegroup settings" window. In this window, click "Leave the homegroup..." A warning will pop up. Go ahead and click "Leave the homegroup."
Step three: You are now presented with a page labeled "Share with other home computers running Windows 7." From here click the link "Change advanced sharing settings..."
Step four: You are now at the "Change sharing options for different network profiles" page. This is where you are going to do the nitty gritty. I'm going to go option by option. Most of these will probably already be configured correctly, but I'll tell you how they should be configured, nonetheless.
Network Discovery: turn on network discovery
File and printer sharing: turn on
Public folder sharing: Your choice. It can be on or off.
Media Streaming: By default, this is off. You can turn it on if you want, but it is not why we are here, so I'm going to leave it off for now.
Password protected sharing: Turn off password protected sharing
HomeGroup connections: This doesn't really matter, since you already left homegroup. However, I allowed Windows to manage my homegroup connections. It seemed easier than arguing.
Step five: Click Save changes. Now close the window that says "Share with other home computers running Windows 7."
Step six: Navigate to a folder you want to share. I am navigating to D:\Movies. First, left click on D:\Movies (or whatever your folder is named) to make sure it is highlighted. Then, right click on the folder. Put your mouse over "Share with" and four options should pop up "Nobody, Homegroup (read), Homegroup (read/write), Specific people." Click "Specific people..."
Step seven: You should now be on a dialog that is entitled "Choose people to share with." Your goal is to share the folder with "Everyone." On the dialog there should be a list of people. This list might include "Administrator," your username, "Guest," and "Everyone." It might only contain a subset of that group. If "everyone" is listed, simply click everyone, then click "Share." Voila, done. If you want to decide whether to keep Everyone as a Reader or change them to a Reader/Writer (or vice versa), read Step eight.
If Everyone is not listed, click the dropdown arrow next to the "Add" button. "Everyone" should be on the list there. Click it, then click Add. If "Everyone" isn't on the dropdown list, you may be able to type "Everyone" in and click Add. Feel free to comment if this is an issue and/or it doesn't work.
Step eight: Once "Everyone" has been added to the list, you have two choices. You can choose to keep "Everyone" as a Reader only, in which case XBMC would be able to read the files, but could not write anything into the folder, meaning it could not correct file names or export nfos and tbns into the folder, if you want that. Or you can choose to change Everyone to Read/Write, using the drop down arrow on the Everyone line. Then XBMC can export, but you have to deal with the danger that anyone on the network could change the files.
Once you've made your decision, click "Share."
Step nine: Repeat steps seven and eight for all folders you wish to share.
Now you can add your sources in XBMC without difficulty, but the guide to XBMC sources and scraping is in the Wiki and doesn't need to be repeated here.
4 Later Addition
If you are having any additional problems, definitely read through the rest of this thread. In particular, uninstalling Windows Live Sign In Assistant and Windows Live Essentials seems to be a useful thing to do.
5 Regarding cyber7's post
I have no idea what all that stuff is. My presumption is that some computers don't have those settings turned on by default. I have had no issue or need to deal with any of cyber7's instructions, but maybe they could be useful to others.