@
Chris_Snow - for new 'books' I typically enter 8-13 cells (2 dates, 3 ints, some tag like strings, etc), so our perceptions are probably quite different.
Have you tried running
1.48.0 on the new box. If you install the 32bit version of 1.48, you'll be using the same libraries and configuration data as the 64bit 3.7. That should give you a feeling as to whether it's a Calibre or Windows issue.
BR