How do I make Windows 7 show Unicode all characters properly, like those in this question?
Right now I just see squares for some of them.
You don't say explicitly but I imagine your question is about a web-browser, most likely Internet Explorer 7. Web browsers attempt to display a web page in a font specified by the web-page or in a font specified in the browser configuration (which can be set to override web-page directives). Sometimes, a web page contains a character for which the selected font has no glyph. The browser will usually attempt to find a glyph in other fonts installed on the computer. If it cannot find a glyph, it typically displays a square box.
Step 2. Then identify which browser you are using to view the Unicode data. Install Firefox and Chrome and compare results.
Step 3. Finally locate a font that contains the characters you wish to be able to view, install that font and re-test by accessing the Unicode test pages with the range of installed browsers.
An excellent source of help is Alan Wood's Unicode Resources
Text editors and Word processors will display a square (or other stand-in character) if the current font does not contain the character. Changing fonts can solve the problem. Unicode has over a million characters. No single font has more than a few tens of thousands (Arial Unicode MS has the most of any common font). Most fonts have a few hundred only. You therefore often have to use mixed fonts if you want to display characters from more than one writing system.
Some good reading matter (mainly aimed at programmers but should be interesting for others)