Tested in Windows Server 2008 Enterprise and Windows XP SP3
1. Download your favorite fonts from Internet
2. (UnZip if needed) Locate your xyz.ttf file
3. Open by double-click it (A font window pops out)
4. Change font type in your desired application (manually input it in setting)
The truth is that when you try to preview the font, Windows temporarily installed the fonts in order to render it.
A very smart hacking indeed.