Do I really need to repeat myself as to why it's a bad idea to do that? Anyway, the program crashes because it is attempting to load all the fonts and basic rendering information into memory, which in turn causes the program to fall over. Also, Adobe products have strict requirements in regards to font support, and some bitmap fonts are known to cause Adobe products to crash because they aren't made to those requirements. I'm surprised you can even run windows if you have the entire font set installed, let alone run Illustrator. Here's a little piece of advice... Backup and flatten your system Reinstall everything from scratch (including updates, office, adobe, etc) Backup the windows font folder using your favourite archive program Extract the 7000 free fonts archive to "C:\Fonts" Use a free font manager like the "The Font Thing", to manage, view and install fonts as needed. Be sure to remove them when you are finished Its also a good idea to backup the windows font folder after installing/upgrading major programs. This is so you have a working copy of the font folder incase you do something silly like copying 7000 free fonts to it. It's recommended that you run windows in Safe Mode as Administrator, when restoring the backed up font folder.