Winforms doesn't support Open Type fonts. So the Windows font mapper found you a substitute TrueType font. It resembles your original font but of course doesn't render the same. Not having ClearType enabled won't improve the outcome either.
Open Type font support in Windows in general is not exactly stellar. You can typically only rely on Adobe programs to support it well, there's no decent fallback for programs that render text with GDI or GDI+. I only know of WPF as a GUI builder tool that support it. Dealing with the gratuitous Adobe product compatibility problems on Windows has a long, long history. And resembles the joy I experience having to use Flash or Reader.