Hi Harry,
Bug confirmed. It happens on all platforms, and happens for all tools irrespective of whether they have documentation or not.
Workarounds: (1) Manually resize Windows Explorer by dragging the border opposite to its docking side (docked at the left by default), or (2) leave the ProcessExplorer window with its extension visible.
This is a regression in version 1.7.4. I'll try to release an update ASAP. Thanks for reporting and sorry for the ugly thing.