Windows is not real time OS, so well, you don't have true realtime processing capabilities in Windows.
With Windows Vista, Microsoft offered a new API that among other thing targeted strict performance, where Exclusive-Mode Streams promised performance close to real-time. This is achieved with a few powerful things working together, including short and exclusive path to audio hardware from user mode components, specific multimedia scheduling. Let me quote Wiki on this:
For audio professionals, a new WaveRT port driver has been introduced
that strives to achieve real-time performance by using the multimedia
class scheduler and supports audio applications that reduce the
latency of audio streams. As a result, user mode applications can
completely govern streams of audio without any code execution in the
kernel during runtime. WaveRT allows the user mode application direct
access to the internal audio hardware buffers and sample position
counters (data in the memory that is mapped to the audio hardware DMA
engine). It allows applications to poll the current position in the
DMA memory window that the hardware is accessing. WaveRT also supports
the notion of a hardware generated clock notification event, similar
to the ASIO API, so that applications need not poll for current
position if they don't want to. WaveRT however works only with PCI,
PCI Express or onboard audio devices; it does not work with USB or
FireWire interfaces which are more widespread in the professional
This new mode of operation opened exciting opportunities for low latency audio processing, such as reported by happy users:
I get perfect rock solid stable audio with 2ms buffers + 0.5ms
latency, compared to semi-stable audio in 4ms buffers (+5ms output
latency), with ASIO.
Depending on whether this real-time approximation is good for you, Windows might still be a good environment for the mentioned task.