Your ISP should set up ulimits for all CGI processes and kill them after (say) 2 minutes to prevent such stuff. You should develop and test not on your production webserver but on a local machine, for example by using VMWare Player or installing and running Apache on your development machine. If you're developing under Windows, you might prefer to go the VMWare route because fork() is broken on Windows and signals don't exist as a mechanism of IPC.

Looking at your code I find it very hard to make out what's going on because you don't use indentation.