A Chinese anti-trust regulator said on Monday it has given Microsoft Corp 20 days to reply to queries on the compatability of its Windows operating system and Office software suite amid a probe into the worlds largest software company. The State Administration for Industry and Commerce (SAIC) questioned Microsoft Vice President David Chen and gave the company a deadline to make an explanation, the agency said in a short statement on its website. SAIC also repeated that it suspected the company has not fully disclosed issues relating to the compatability of the software and the operating system. [A] special investigation team conducted an anti-monopoly investigation inquiry with Microsoft Vice President Chen Shi (David Chen), and required that Microsoft make a written explanation within 20 days, the SAIC said in a statement on its website.