Sometimes when we want to login windows XP there is a notification the security log on this system is full. Only Administrator can log on to fix the problem. The other user cannot logon to the windows, as picture below.
To solve this problem, we need user Administrator and Password (for this computer)to logon windows. Then Right click at My Computer > Manage, there is display Computer Management. Click System Tools > Event Viewer.
Then right click on Security > Clear all Events.
Choose No, if there is notification to save.
And then the system will clear all logs at event viewer.
Restart the computer and try to login with other user name.
Lets see the result is success.