Step 1. Sharing something
Get to the "File Sharing" dialog by either:
a) Share with
- Right click on the folder you wish to share
- Click on "Share with"
- Click on "Specific people..."
b) Properties
- Right click on the folder you wish to share
- Click on "Properties"
- Click on the "Sharing" tab
- Click on "Share ..."
Now you should arrive to a screen that looks like this.
Step 2. Sharing with who?
Select "Everyone" if you want no fuss, no password sharing. The XP computer will be able to access your shared files across the network without any issues.
If you want to allow access to only a specific user, then the XP machine will be asked for a password before it is allowed access.
Click "Add" to add them, and click on the dropdown to modify what permissions they have (ie. Read and write).
Click "Share" to apply the settings and begin sharing.