Hp mini with intel haswell Celeron is indeed capable running Windows, but don't performance wise its pretty light. Office and Internet only.
Running games? Sure, if you're talking about Solitaire and minesweeper. It will not make to run Crysis for example.
Asus chromebox has identical hardware, costs less and with changes can run Windows or htpc if wanted so.
As for pi2 - for htpc usage i expect difference to be minimal.
Pi2 could run os with gui desktop, but limited to Linux only.