When you do sample rate conversion the quality of that conversion, especially the digital filtering varies. The conversion in Windows is not a terrific algorithm. The filters in the player I suggested and also some other players is of far higher quality.
http://src.infinitewave.ca/
Look here. Though these are down-conversions you can see quite a range of quality in the conversion depending upon what is used.
In the case of HQ player the filtering is complex and of high quality using many taps. If you upsample to the max rate your DAC can do then it does less internal upsampling and filtering. This lets the player software use better filtering for conversion of 44 khz material. Less aliasing, less noise, better results. If your DAC has a very poor analog section it may swamp the benefit, but most decent ones are good enough.
Looking at that link the signalyst one: "signalyst 2.9.1 (sync)" seem to definitely be the one of the best overall (not that any DACs have a noise floor down at sub 180db, but still..).
Do they have the default windows up-sampler tested in there? Couldn't see it?
Some of them are just terrible, eg:
Mentioned signalyst 2.9.1 (sync) for reference
With 44.1khz sampling rate there should get a bit of stuff above 22khz, judging from the impulse test it shouldn't be too bad.
Do these test applying when up-sampling using the same method as well?