hello there i have just had the same problem as well among others but here is what some person at microsoft told me to do via email since this was after instaling the (KB936929) winxpservice pack 3 hope this hels in some way
Thank you for contacting Microsoft Online Assisted Support. As I understand it, after installing Windows XP Service Pack 3 (SP3), the system cannot be booted into.
here is what was said and asked
Before moving on, I would like to confirm if the system is preinstalled by the computer manufacturer.
If this is the case, I would like to explain that this issue can occur if the image of an Intel-based computer is deployed on a non Intel-based computer.
Considering the current situation, I suggest trying the following steps to check if we can make any progress:
Suggestion 1: Disable the Intel PPM service using the relevant command:
1. In Safe Mode, please go to Start, Run, and type CMD. Click "OK" to open a DOS like command window.
2. In the window, please enter the following command:
sc config intelppm start= disabled
3. Press the Enter key to execute the command.
4. Restart the computer to check the result.
If the issue persists, let’s try to modify the relevant registry keys to disable the IntelPPM service
Suggestion 2: Modify registry keys to disable the IntelPPM service
1. Please go to Start, Run, and type REGEDIT. Click "OK" to open Registry Editor.
2. In the left pane, please locate the following key:
3. Right click the above key and choose Export. Please save the file as backup in .reg format. If any unexpected issue occurs, we can restore the registry keys.
3. Highlight the above key and double click the subkey named "Start" in the right pane.
4. In the open window, please change the value to 4.
5. Click "OK" to save the change.
6. Quit Registry Editor and restart the computer to check the result
hope all is ok now good luck