How to Reset the Default System Security in Windows XP

1. Click 'Start' and then click 'Run.' Type 'cmd' and then press the 'Enter' key.
2. Type 'secedit /configure /cfg %windir%\repair\secsetup.inf /db secsetup.sdb /verbose' and then press the 'Enter' key.
3. Click 'Start,' and then click 'All Programs.'
4. Click 'Accessories,' and then click 'Command Prompt.'
5. Type 'net users' at the command prompt, and then press the 'Enter' key. A list of user accounts on your computer will be displayed.
6. Type 'net localgroup users [accountname] /add' (substitute your user account name and do not use brackets), and then press the 'Enter' key. Do this procedure for each account name on your computer that is missing from the list displayed in the previous step. This will reset the default system security in Windows XP.