I am working as a computer technician for residential and small businesses. I like to use sfc/scannow but most clients do not have their operating disks. Is there a way for a SMALL pc repair business to gain the disks without having to buy every version out there to be compatible with my client's versions. Any help or suggestions are really appreciated...

Any reason it would not run from the cmd/run command?. Runs on my Vista from the cmd, after I requested it to Run As Administrator.

That's a good question

Firstly it's sfc /scannow (with a space after sfc )

Regarding Windows CDs. I agree there are many versions that technicians must carry with them
But, in saying that. A technician should always use the customer's Windows CD

If the user does not have a CD, they are requested to purchase one

In your case, if you intend to help others, you could copy your own CDs (Note: Backing up your own Windows CDs is not unlawful; but I'm also hinting to somehow get a copy of different Windows CDs for yourself, before helping others )