Windows file sharing is horrible. Particularly with XP Home. Is that what you're using?
Have you ensured you are properly sharing a folder on the laptop? If so, I recommend this: ensure that you are using the same username and password on both machines, and ensure that the share permissions reflect this. If it still doesn't work, try going to Windows Explorer and in the file bar, type "\\laptop\share", where laptop is the name of your laptop in the workgroup, and share is the name you gave to the shared folder on the laptop.
Report back!