I have 30 systems in a LAN . My users need to login as domain user from their XP clients and store their files in the Linux server. They should not be allowed to store in local machine and also should be granted a particular size of space in server.

what are the procedures to be done in linux server and

just like in windows we access shared files in by typing in run command

\\192.168.0.1 is there a provision to view shared files from xp to Linux

check about samba
http://us3.samba.org/samba/

configure samba server and access your file by window xp

And if you do not want them to store files locally then you will need to make permissions on machines that way. Samba will only help you in copying files from windows to linux.

configure samba server for sharing files in linux server & access them from windows xp machine.

install fallowing package


samba
samba-common
samba-client
samba-swat.

then
vi /etc/samba/smb.conf
[share]
sharname= abcd
share directory= /abc
read only = No
browseable = No
create mask = 0644
directory mask = 0755

service portmap start
service smb start

then access your samba server from window xp.

this config is an example, of many configuration types.
And is written for Fedora, or RHES, as it seems.

However, the easiest way is to also install a gui package, to visually configure the samba system. (SWAT is one, but requires a webserver)
Check your repository of your distribution, by searching for samba..

Samba is not that hard to setup, and has allmonst all possibilities of win2000 and part 2003 server. Including policies, startup scripts deployed on the client, domain server, memberserver etc etc..
It mainly up to you, what type of samba config you want.