keylogger trojan

Does anyone know what the file DLTIME.dll is used for and if I can reload this file? My friend’s XP computer had a Norton error stating there was a keylogger-trojan virus on the DLTIME.dll file that could not be removed. I tried to fix the problem by deleting the c:\winnt\dltime.dll file but now get the following error message whenever they boot the computer:

svchost.exe – Unable To Locate Component
This application has failed to start because dltime.dll was not found. Re-installing the application may fix this problem.

I need to know if DLTIME.dll can be copied back or what program to re-install? Thanks!