k first and foremost read this ::
In Linux, everything is stored as a file. Most users are familiar with the two primary types of files, text and binary. However, the /proc directory contains files that are not part of any file system associated with any physical storage device connected to your system. Instead, the virtual files in /proc are part of a virtual file system.
The virtual files in /proc have unique qualities. Most of them are 0 bytes in size. Yet when the file is viewed, it can contain quite a bit of information. In addition, most of their time and date settings reflect the current time and date, meaning that they are constantly changing.
Both applications and system administrators can use /proc as a method of accessing information about the state of the kernel, the attributes of the machine, the state of individual processes, and so on. Most of the files in the directory, such as interrupts, meminfo, mounts, and partitions, provide an up-to-the-moment glimpse of a system's physical environment. Others, like file systems and the /proc/sys/ directory provide software configuration information.
To make things easier, files that contain information covering a similar topic are grouped into virtual directories and sub-directories, such as /proc/ide/ for all physical IDE devices.
now that that is said, you can now see why you cannot go and create a acpi directory....
try using apm...
and then try shutting down
acpi is basically used for multi-processors and laptops...