Ms Reller, a 12-year veteran of Microsoft, runs the financial and marketing side of the Windows unit, while Julie Larson-Green runs the technical side.
Microsoft hinted that Sinofsky's successors would stress integration and collaboration between business units, especially Windows and Office, which has been strained in the past.
"I am very happy with where our relationship is with the Office team," said Ms Reller. "Both Julie and I have worked closely with the Office team. We worked closely together when Steven (Sinofsky) was here and even closer now."
Ms Reller said collaboration was already happening under Mr Sinofsky, citing the creation of Bing, Xbox and Office apps for Windows 8, and close co-operation with Microsoft's server and tools unit, which enables Windows 8's "cloud" services to operate.
"More has not changed than has changed," said Ms Reller. "We probably had a day of getting ourselves oriented and maybe a few weeks to get fully oriented, but things are moving."
Announcing Mr Sinofsky's departure in November, Microsoft chief executive Steve Ballmer wrote an internal memo stressing a new goal to "drive alignment across all Microsoft teams," suggesting co-operation had not always been a success in the past.
"Steve's reference was, 'Let's take that base (of collaboration) and just keep going," said Ms Reller. "And that's happening."
Microsoft spent hundreds of millions of dollars promoting Windows 8 and Surface last quarter, but consumer interest at third-party stores such as Best Buy in the US tended to focus on Apple and Android products, according to a Reuters survey of shoppers in mid-December.
Some in the PC industry have complained privately that Microsoft has not done enough to train sales people or educate consumers on the new range of devices running Windows 8.
"I think we can do better and we'll work with them (retailers) to do better," said Ms Reller. "That's not a criticism of our retailers. But we are definitely going to do more at retail to make that experience better."
Overall, Ms Reller was happy with progress in the 90 days or so since Windows 8 launch.
"This is a solid start. But we are just getting started," she said. "We have a lot of reasons to be optimistic."
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