Technical question about Dell System and Data Back-up and Factory Default.

I have been asked to back-up my system data in order for Dell Technical Support Engineer (Harry) to do a restore of my PC to the Factory Defaults. The other less intrusive methods that he tried engineer were not sufficient to resolve my problems. Give this, I have a technical question. Can I use the Dell System and Data Back-Up programs, to a USB hard drive? I assume the answer is yes, however, my concern is that if the PC is restored to the Factory Default, presumably an image copy restore process, then, if I run the Dell System and Data Back-Up Restores programs, might this process put back the corrupted system files that were causing the problems and we are back where we started? Please advise on how this back-up process should be done. I have always backed up my data but never had to go through this process.