Linux & Windows

Well for Telnet,

use the command :
telnet [host name i.e. the computer's network name] and u will connect to ur system,

Now Use these commands :
Command
What this command does....
ls This command will list all of the files and directories within the current directory.
cd <directory> This command will change your current directory to the directory you specify. An example would be that "cd public_html" would take you into your public_html directory.
mv <filename> <location> This command will move a file from its current location within the current directory to the directory you specify. For example, let's say you are in your public_html directory and you want to move the file "links.cgi" into your "cgi-local" directory. At the prompt type "mv links.cgi cgi-local.

chmod XXX <filename or directory> This command will set the permissions on a file or directory to whatever you specify. The "XXX" would be replaced by actual numbers, such as 644. For example, if we wanted to set the permissions on our links.cgi file in our cgi-local directory, we would first go into that directory then type "chmod 755 links.cgi" at the prompt.

rm <filename or directory> This command will delete the filename or directory you specify in the current directory. If we wanted to remove the directory named "user", we would type "rm user" at the prompt.

man <command> This is one of the most helpful commands for new users. It allows you to see all of the different options for a particular command. For example, if were were to type "man ls", we would then see all of the different options available for the list (ls) command.

traceroute <domain> This command will perform a traceroute on a particular virtual domain to see how many hops it takes to get from your location to the domain specified. An example would be "traceroute yahoo.com", which would show us how long it takes for packets to get to yahoo.com and how they get there.

whois <domain> This command will display the current InterNIC record including administrative, technical, and billing contact for a particular domain if it is already owned.

Source : Help Quest

Use Pico to edit a few kinda files (basic edit)
pico <filename>

ANd to talk, type
talk <username/login name>

Hope this helps,
Qwerty

hi there
you can connect those two computer on with winxp and other with linux by using a server program commonly known as SAMBA. search it on goggle i am sure u will find a solution

if you want to run commands through command prompt in windows then you can use telent or ssh (which is more secure ) however telnet is available by default and if its like the setup u mentioned you can probably use telnet like the @QwertyManiac describes.
if u want to get a graphical control of linux ( copying files, moving folders, etc ) i suggest u use samba as @popper1987 suggested.
My suggestion is to use both
ps: you can also use VNC to get the linux desktop on windows system. site is www.tightvnc.com

samba
this should help...