How make modprobe find my kernel module?

[Parmenides]

Hi,

    I have write a 'hello, world!' module which is in a directory
rather than the kernel source tree. I compiled it by:

                       make -C /usr/src/linux SUBDIRS=$PWD modules

and installed it by:

                       make -C /usr/src/linux SUBDIRS=$PWD modules_install

I find it was installed at /lib/modules/2.6.34/extra. Then, I invoked

                        modprobe hello.ko

to load this module, but get a message:

                        FATAL: Module hello.ko not found.

It seems that my module is not in the modprobe's search path. Is that
true? If so, how can I configure its search path?