Treeline is a very nice cross-platform (Win 7, 8; Linux) hierarchical notes manager. It is similar to Treepad (as the author himself notes).

As for OP's requirements:
Freeware
Not ancientware (must have been updated during the last 3 years)
Support italics/bold text | and more besides
Windows 7 SP1 compatible
Can successfully import Treepad Lite files | Not sure - Treeline can import "plain text, tab-indented text and tab-delimited table files" as well as "generic XML files" (and import/export its own HTML); Treepad Lite can export (according to the online documentation) HTML and a "Treepad Lite file". There might be something compatible in there, but I'm not sure.
It ticks enough boxes to be worth investigation, at any rate. I use it from time to time under Ubuntu and enjoy having it in the "toolkit".