She is the default "ghost" of "Are Igai no Nanika with Nin'i".

Nanika is so called desktop accessory program.
When the program was launched, there appear a character called "ghost"
and her (ghosts are usually female characters) buddy.
The program is running in background, and the users can run other programs.
While nanika is running, the ghost and the buddy talk jokes.

Short History of Nanika (Ukagaka):

The original program of "Nanika" is "Personaware with Haruna" made by Nakanishi Takumi.
This is desktop accessory software.
When the program starts, a secretary, Haruna, appears.
She greets users when the program starts or when it ends,
tells time, shows today's schedule, and so on.
This program was released for free, but it became shareware later.

To improve its function, "Nise Personaware with Nise Haruna"
(Pseudo-Personaware with Pseudo-Haruna) was made by Kuroi Sabato.
The name suggested his complaint against Personaware.
But, in order to avoid legislative conflict in future,
he changed the name to "Are Igai no Nanika with Nin'i" (Something other than that with an arbitrary).  
The name was changed to "Nanika(kari)" later, and it is called "Ukagaka" now.
(It may be because "Ukagaka" looks like "Nanika" in Japanese) *

He left the character nameless and let the users change her name arbitrarily (Nin'i).
Therefore, the software was named "...with Nin'i".
But users began to call her name "Nin'i", and the name remained.

The newly developed software had features that the original Personaware didn't have.
For example, AI-function is welcomed by many users.
However, the most attractive feature was to let the users make their own characters easily.
With this feature, numerous characters, which is called "Ghost", have been made.
Exactly speaking, the "Ghost" indicates the personality (the conversations and the responses),
and its appearance is called "Shell".
In many cases the ghost is distributed with its own shell.
However, it is possible that another person makes the other shells.
Therefore, the users can change the appearance of the ghost,
for example, winter coat into summer bikini.
More drastically, you can even replace the shell with the bit map images
taken from the game (if the copyright permits).

A typical ghost is a pair of a girl and a creature.
Of all the ghosts in history, the most famous one is probably "Mayura & Kuro Unyu".
For a long period, Nanika was distributed without default "Shell".
During this period, she has been introduced by many computer/game magazines,
and it helped "Nanika" become popular although it had no default shell.
However, because the author stopped to release Mayura in public in 2003,
it is hard to obtain "Mayura" now.

(masahiko) Wed, 21 Sep 2005 10:14:54

This had been published on AnimeNfo (« exists no more)
何か (Nanika) - somehing, anything

伺か (Ukagaka) - no official Kanji!
Google can't really tell. It's a pun!
Maybe "something weird going on"/"...happens"?   (weird, strange, odd)

Some people misunderstand it as pictures and manga too,
so Google lists them all besides pages to this software...