adobe photoshop - Can't see all the font styles installed in Windows 7

I've installed a font that has different styles (bold, italics, thin, medium, ultra and so on...), but I can't use them all because I can't see them in Photoshop. The fonts are installed, but seem in some way "overlapped" by windows.

If I open the Windows fonts dir I can see only one style. If I delete it, then a different style appear and so on.

Anyone has a solution for this problem?