The file system in Windows XP is based on Windows NT and Windows 2000, many features are new to users of Windows 9x.

In Windows 9x, you can assign a password to a shared disk or folder, so that only people who know the password can gain access. That works well in a small home network where, for example, Mom and Dad know the password to the family's financial data, but Junior doesn't. But it isn't practical in a large corporate network, where Windows XP Professional is likely to be used. It's hard to keep a password secret in a large company, and changing to a new password requires giving it to everyone who needs to use it.

Windows XP Professional replaces password-based security with two alternatives:

  • "Simple File Sharing" is enabled by default on Windows XP Professional systems that are members of a workgroup (typically used in small networks) rather than a domain (typically used in large corporate networks). For full details, see "How to share files in Windows XP (Simple File Sharing)?". There are no passwords or access restrictions and, with one exception described in the article, everything that's shared is accessible by everyone on the network.
  • By disabling Simple File Sharing, you can specify an "Access Control List (ACL)" for each shared disk or folder. The ACL specifies which users are allowed to have access. For full instruction, refer to "How to share files in Windows XP (Access Control List - ACL)?".