How do I... Secure Microsoft Windows XP Professional?

Rename the Administrator account.

Step 12: Always use NTFS
These days, there is almost no reason to not use NTFS. FAT and FAT32 are supported in Windows XP, but are not nearly as flexible as NTFS, nor are they as secure. Nor do FAT and FAT32 allow for partitions as large as those allowed by NTFS. For all of these reasons, you should use NTFS whenever possible. If you have a Windows XP system running with FAT or FAT32, you should convert the non-NTFS partitions to NTFS.

To do so, from a command line, use the command:
convert (drive letter) /fs:ntfs

This is a one way transition.

Step 13: Rename the Administrator account
Every Windows XP installation has an Administrator account. Although a hacker can use other methods to obtain the name of the primary administrative account, by renaming this account to something else, you make it that much more difficult for them. To rename the Administrator account:
  1. Click the Start button.
  2. Right-click My Computer and, from the shortcut menu, choose Manage.
  3. When the Computer Management window opens, go to Local Users and Groups | Users.
  4. Right-click the Administrator account and, from the shortcut menu, choose Rename.
  5. Type the new name you want to use for the Administrator account.
As an additional step, you could also create a dummy account named Administrator that actually has no rights on the system. Again, this will not deter determined hackers, but is another wall you can throw up on their trail.

Step 14: Use Group Policies whenever possible
Group policies provide a large number of security options and make it easy to secure all of the Windows XP computers in your organization in one fell swoop. Learn everything possible about Group Policy and then use this feature to secure your organization. Visit Microsoft's Windows Server Group Policy site for tutorials, information and labs related to Group Policy.

These 14 steps will go a long way toward protecting your Windows XP system from outside attack. While there are other things that you can do, these techniques are a step in the right direction.