This is becoming a more common problem on Windows XP PCs. It appears to have been corrupted by a faulty update.
To fix the issue, press CTRL-ALT-DEL at the blank screen and start the task manager. From the Task Manager, select File, New Task (Run).
In the Task windows, type CMD, then press the OK button.
The error message will appear a few more times, but the Command Prompt will eventually appear.
From the command prompt, type CD C:\WINDOWS\SYSTEM32\DLLCACHE
Then type COPY IERTUTIL.DLL ..
This will copy the correct version of iertutil.dll to the C:\Windows\System32 folder.
If the file is not found, you can type in DIR C:\WINDOWS\IERTUTIL.DLL /S
A list of files and locations will show up. You can copy the files from any of those folders.
After this, reboot the system and the problem showld be fixed.