Dell STService has stopped working - STString.dll not found

Attached file contains screen dumps of observed errors.

Recently I have been getting the following error message on login (Vista Home Premium SP2, build 6002)...

STService - Unable to locate component

This application has failed to start because STSring.dll was not found.

Re-installing the application may fix this problem

STService.exe was found in C:\Program Files\Dell DataSafe Local Backup\Components\Scheduler\, and 

STString.dll was found in C:\Program Files\Dell DataSafe Local Backup\Components\AppDrv\

STservice service is not shown in Services.msc

I have not consciously moved or deleted any of these files or components - I have had no reason to.

Recently the warranty on my Dell PC (Inspiron 530, BIOS 1.0.18) has expired - could this have anything to do with it?

I don't know where to go to get the software for re-installation - can anyone help?