I have a LAN running RHEL 4. I have connected a windows xp machine onto that LAN and want to copy some 100 gb data on to any of the linux boxes having free space. What could be the best solution for that including smb or ssh. I dont have any security problems. Please refer me to simple steps or any HowTo.

scp or rsync I feel would be the best.

If the XP computer is the USER computer and a decent Linux Distro is the Administrator computer (one head of the network) then the Administrator (head) can see all the files provided XP is seeing Linux correctly. Then the Administrator simply goes to network then chooses the PC with files then it will open all the folders on Drive C: on the XP one. Then you should see a folder saying your name (ex B. Bob Slingblade") inside is all the user files then highlight whatever you need right click copy.
Go back to Network and look at the other PC's and paste the files in the user account. It will take a while to copy.

Alternatives:

Lots of CD or DVD
Jump Drive having to transfer files in little bits
or External HDD.

You could copy the files to a samba share on one of the Linux hosts. Then copy them to the other linux machines using a script, which does the same for each machine, or use rsync or scp.

Also look in the info manual for tar for copying a large number of files (such as the contents of a drive) by piping the output of tar to a mounted directory or using ssh to run tar on the destination to extract them where you want.

tar -C /source/dir tar -cf - . | ssh user@host 'tar -C /destination/dir -xvf - .

This works best using public key encryption, and then using ssh-agent & ssh-add to unlock the private key on the ssh client before running the command.