Some useful information. Your Windows XP computer is more safe if you don’t set any password at all than using some weak password like "abc123" which can be easily guessed by hackers.
Using a blank password (or no password at all) makes your computer more secure because Windows XP accounts, that are not protected by a password, cannot be accessed remotely over the network or the Internet.
You have to be physically infront of the computer in order to get in. Due to this default behavior, it is better to leave a blank password assigned to an XP account rather than assigning a weak, easily guessed password.
An official guide from Microsoft on Password strength therefore suggests using blank passwords on Windows XP machines when the following criteria are met:
• You only have one computer or you have several computers but you do not need to access information on one computer from another one
• The computer is physically secure (you trust everyone who has physical access to the computer – like your family members)
The use of a blank password is not always a good idea particularly when the computer is not in a secure location. For example, a laptop computer that you take with you is probably not physically secure, so on those you should have a strong password.
Update: If you want to access your XP Professional computer over the network ever after the password is blank, run gpedit.msc in the Run box and disable the setting "Limit local account use of blank passwords to console login only" available under Local Policies.