All other fonts only contains few ranges of characters (for example Greek characters or Japanese characters, but rarely both at the same time). In this case, CATIA Symbol font is intended to provide characters for some symbols (a very small subset of all possible characters). Straightness symbol is not part of this font.
@koiyu: When there's an internal naming conflict, the OS presents the first one it comes across as 'the font' and ignores the rest. Delete that one, and the next one on the list then shows up. It's a fragility in the OS's handling of fonts, basically. It would be better if it threw an error so the user would at least know what was happening. Neuratron photoscore ultimate 8. Mac OS has a similar problem which has driven many a typographer to drink: e.g., an inadequate system font can't be replaced by a real font with the same name (since Leopard, iirc). – Jul 27 '11 at 18:55.
The source of this problem is malformed font files. The internal names of the fonts are in conflict and the flags that indicate connections between the different font files in a typeface family (Regular, Bold, Italic, Bold Italic, etc.) are missing. The terminology is awkward. Technically and historically 'Foo' is a typeface and '18 pt Foo Bold Condensed' is a font, but in the era of personal computers the definitions have blurred: a typeface is now often referred to as a 'font' (even though you'll buy a particular style of that typeface as a 'font' in any online store), particularly among non-typographers. The variations tend to be called 'styles.' People coming newly (last 25 years or so) into design are so used to scaling a font in software that they forget every size of every style of a typeface was once drawn and made individually.
For a regular application (non-professional) to give you the usual 'Regular, Bold, Italic, Bold Italic' choices, the font files themselves must be individually named internally and the fact that they are associated is a specific internal flag. It's these internal flags that allow you to create bold or italic text with a keyboard shortcut or style dropdown -- the Foo Bold font file tells the OS 'I am the Bold version of Foo,' and so on.
You have a situation where all the individual font files have the same internal name, so Windows can't differentiate them. You see exactly one font (style) in a family; delete it, and you see another one, and so on. In Word, Open Office, etc., that's probably all you'll see.
(Arial Narrow famously suffered from this problem because of an error in creating the files -- it just wouldn't show up at all, or would never show up as an available style for Arial.) Most non-graphics applications natively understand only the usual four fonts in a family. Additional members (narrow, thin, black, extended, etc.) show up as separate typefaces. More sophisticated applications such as Photoshop or InDesign know how to read the association flags in a set of font files and can display all the variations in a single dropdown.