Depending on your interpretation of those definitions, either Multi-programmed or Timeshared; none fit exactly.
In Windows (or Linux or Mac os etc) the operating system runs multiple tasks or programs as the same time by switching sequentially between the running programs anything from around a hundred to a thousand or more times each second. It's fast enough that all appear to run simultaneously in human terms.
That is how both multi-programmed and timeshared systems operate.
Multiprogramming was originally created to allow one or more programs to execute while others were being loaded or the results output, back when punch cards or paper tape were used.
One operator working on multiple programs; it fits in some ways.
Timesharing allowed many users to share one computers resources, with each running their own programs.
An MS Windows system only has one user at a time, but running many tasks and optionally multiple programs in different windows.
If you consider each desktop program windows as a user connection, it equates to timesharing.
Neither is a perfect fit.
Others:
A Distributed system allows multiple separate computers to pool resources and in some was act like a far more powerful single system.
Real-time means the system is designed to interact instantaneously with external events. Some people may claim Windows does this, but as a programmer I can say categorically Windows is not a real-time rated system. Real-time means microsecond response, not 'usually within a few milliseconds', which is how windows reacts.
Embedded means the operating system is installed in ROM, EPROM or FLASH Rom etc. - it's effectively 'built in' the device memory as supplied - like phones and tablet PCs.
There are special embedded versions of XP etc., but the normal PC versions are not embedded.