Thank you for your post.
Just so I'm clear, the database file is being hosted on a Windows XP (SP3) computer, and FileMaker Go is unable to see the file remotely? Is this on an iPad? iPhone? Is there any firewall issue with the Windows machine? Is FileMaker network turned on at the host machine? Are you referencing the IP Address? Are there any other hosted files on the Windows machine that aren't showing up when you tap the Local Network Hosts icon in the upper right corner of FileMaker Go? Do any other devices have problems connecting to the host machine? Or, is this the only iOS device being used?
Any other information you can provide may be helpful.