scandisk – should run from Dos or from w

When I try to run scandisk on my C: drive from Windows 95 it hangs up. I believe it is because the swap file is open. If I disable the swap file can I restart my PC?
I ran scandisk on the C: drive from the dos prompt and it didn’t find any errors.
I want to defrag my drive but want to check for errors first. Does running scandisk from Dos show an accurate picture of my drive?