I am using nmap -O and have the result below:
OS:SCAN(V=5.05BETA1%D=8/23%OT=22%CT=1%CU=42341%PV=N%DS=0%DC=L%G=Y%TM=4A91CB
OS:90%P=i686-pc-linux-gnu)SEQ(SP=C9%GCD=1%ISR=CF%TI=Z%CI=Z%II=I%TS=A)OPS(O1
OS:=M400CST11NW5%O2=M400CST11NW5%O3=M400CNNT11NW5%O4=M400CST11NW5%O5=M400CS
OS:T11NW5%O6=M400CST11)WIN(W1=8000%W2=8000%W3=8000%W4=8000%W5=8000%W6=8000)
OS:ECN(R=Y%DF=Y%T=40%W=8018%O=M400CNNSNW5%CC=N%Q=)T1(R=Y%DF=Y%T=40%S=O%A=S+
OS:%F=AS%RD=0%Q=)T2(R=N)T3(R=Y%DF=Y%T=40%W=8000%S=O%A=S+%F=AS%O=M400CST11NW
OS:5%RD=0%Q=)T4(R=Y%DF=Y%T=40%W=0%S=A%A=Z%F=R%O=%RD=0%Q=)T5(R=Y%DF=Y%T=40%W
OS:=0%S=Z%A=S+%F=AR%O=%RD=0%Q=)T6(R=Y%DF=Y%T=40%W=0%S=A%A=Z%F=R%O=%RD=0%Q=)
OS:T7(R=Y%DF=Y%T=40%W=0%S=Z%A=S+%F=AR%O=%RD=0%Q=)U1(R=Y%DF=N%T=40%IPL=164%U
OS:N=0%RIPL=G%RID=G%RIPCK=G%RUCK=G%RUD=G)IE(R=Y%DFI=N%T=40%CD=S)
How can I find the most likely OS on this scaned computer. How can I interpret this result, And which are the indicators for and against this guess.
Nmap prints this kind of fingerprint when its own database of fingerprints does not contain an exact match. You can learn more about this fingerprint in the documentation section, "Understanding an Nmap Fingerprint".
From a more practical standpoint, you can try to improve Nmap's chances of matching, or have Nmap print more aggressive guesses. To get a better match, the first and most important thing would be to update your version of Nmap. The fingerprint says you are running version 5.05BETA1, which would have been release sometime in 2009. The current version of Nmap will have hundreds more OS matches, especially for newer operating systems.
When Nmap doesn't have an exact match, it tends to avoid printing any information, to avoid guessing incorrectly. If you would rather know what its best guesses were, you can use the
--osscan-guessoption, and it will print out something like: