adduser not found

[Sumit Ahuja]

Hi,
I am a newbee on linux. I have two questions:
1-) I didn't find adduser or useradd command to add users. I am currently having
command line access to my machine only so I cannot use graphical utility to add
user.
2-) I have been strangly seeing some excessive amount of disk usage on my
account. I checked my account and it shows as if I am using 100Gb space but
once I calculate the size of all the visible directories it comes out 5Gb only.
I checked all extenstion .*, *.*, *...Any way to get hold on this?

Thanks in advance!
--Sumit