Can you post a side-by-side screenshot?
Lightroom is color managed and the Windows desktop is not, so there will inevitably be some difference. Lightroom should always be more accurate.
However, if you have a defective monitor profile (possibly through Windows Update), that will affect Lightroom only. Why that is, is explained here: https://forums.adobe.com/message/8121247#8121247
I have not purchased a new screen just computer tower so the calibration should be the same as before.
So a different Graphics Card then, calibration takes the whole graphics system into account.
Unlike the rest of Lightroom, the import dialog is not color managed (as far as I can tell), and it will also display the jpg previews embedded in the raw file, not the converted raw files.