Former Newcastle striker Ranger scored his first goal for his new club, netting from close range seven minutes before half-time following good work from Pritchard on the right.
And Pritchard scored in injury time when he squirmed away from Clint Hill before nudging the ball past keeper Brian Murphy.
Bond, speaking in place of boss Harry Redknapp, who is on crutches following a knee operation, conceded that it had been a dismal night for the west London club.
He said: "We did put a strong side out and wanted to build on the results we've had this season and keep the momentum going.
"It wasn't a game we wanted to take chances with. With wanted to progress but it turned out to be hugely disappointing.
"We upped the tempo in the second half, but ultimately the damage was done in the first half.
"We knew Swindon would play good football and they did, but in all fairness I think we allowed them to play and as a consequence we never got our game going.
"It was too slow. We didn't play quickly enough when we had the ball. We picked it up in the second half but we got what we deserved. It was a fair result.
"We had a goal ruled out for offside which may not have been offside and we also might have had a penalty for a challenge on Shaun Wright-Phillips.
"But in all honesty we're clutching at straws there. Swindon deserved to win and it's not been a good night for us,
"The manager knows what areas he wants to strengthen and I don't think anything will have changed after that game."
The only real bright spot for Rangers was the performance of winger Mo Shariff on his debut.
Brought on as second-half substitute, the youngster created a couple of openings and worried the Swindon defence with his pace.
"We haven't had a chance to see much of him play so it was good to get a look at him," said Bond.
"He's a young player who wanted to show Harry what he can do and I think he did that."