1. Did you make any changes to the computer recently?
Method 1.
a. Click Start and then Run.
b. Type gpedit.msc in the Run dialog box.
c. Press ENTER on your keyboard.
d. In the Group Policy Editor navigate to:
User Configuration > Administrative Templates > Control Panel > Display
e. Double-click Hide Screen Saver tab.
f. Select Not Configured.
NOTE: If the Screen Saver tab is missing on a per User account basis then the above method will not work, you will need to use the Registry Editor to remove the Group Policy.
Method 2.
Manual Steps Using Windows XP Registry
Registry Disclaimer:
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
How to back up and restore the registry in Windows:
http://support.microsoft.com/kb/322756
a. Click Start and then Run.
b. Type regedit.exe in the Run dialog box.
c. Press ENTER on your keyboard.
d. Navigate to:
HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System
e. Right-click NoDispScrSavPage to select Modify.
f. Change the value to 0.
g. Navigate to:
HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\System
h. Right-click NoDispScrSavPage to select Modify.
i. Change the value to 0.
j. Quit the Registry Editor (Regedit.exe).