1. Passwords should not be words found in the dictionary.
2. Your password's length should be at least 8 characters long and has no repeating characters like ab22xy.
3. Passwords should be composed of alphanumeric characters, meaning that it contains both letters and numbers or even non-alphanumerics.
A word of caution before you try the following trick: Always note down the generated password as it may change your local Administrator account to that value.
The XP password generator can be used from either the Windows Command prompt or directly from the Run Dialog.
Open the Run dialog [Start->Run or Win+R] and type the following DOS command:
cmd /k net user administrator /random [There's a space between the words administrator and /random]
A very secure but random password would be displayed on the screen. Make sure you write it down somewhere as it won't be possible to generate the same password combination once the DOS window is closed. However, if you are not satisfied with the generated password, you can again type the following command in the open DOS window to get another password.
net user administrator /random [There's a space between the words administrator and slash before random]
The process can be repeated any number of times until you get the style of password you were looking for. While these passwords may be tough to remember, they can be a nightmare for password cracking programs.
Microsoft Windows XP Inside Out also mentions this and few other Windows XP security tips.
Original Source: Smartbro Blog [Thanks Shahrzaad]