Wait... Are you saying that there's SOFTWARE out there called "Flushing DNS" that purports to twiddle with your DNS magically to "make it better" somehow?
'Sounds like "virus bait" to me, and searches I did didn't make it look like anything helpful that really IMPROVES your machine.
There ARE reasons for flushing your DNS cache from time-to-time, but they're rare, they depend on your Windows version, and really don't do much.
Post or PM me your Windows OS version and I can point you to Micro$oft's step-by-step instructions for flushing your DNS cache.