Clustering technique

[Luca]

Dear all, excuse me if i post a simple question.. I am trying to find
a software/algorythm that can "cluster" simple data on an excel sheet

Example:
                Variable a   Variable b   Variable c
Case 1        1                   0              0
Case 2        0                   1              1
Case 3        1                   0              0
Case 4        1                   1              0
Case 5        0                   1              1


The systems recognizes that there are 3 possible clusters:

the first with cases that has Variable a as true,
the second has Variables b and c
the third is "all the rest"

        Variabile a    Variabile b   Variabile c

Case 1     1               0            0
Case 3     1               0            0

Case 2     0               1            1
Case 5     0               1            1

Case 4     1               1            0


Thank you in advance