If you're in the BIOS look for something called PXE in the BOOT options . Mark PXE boot to disable .
If this is a Dell laptop try these steps :
1 Turn on your system.
If your system is already on, shut it down and then turn it on again.
2 Press <F2> immediately after you see the following message in the upper-right corner of the screen:
<F2> = System Setup
If you wait too long and your operating system begins to load into memory, let the system complete the load operation, and then shut down the system and try again.
NOTE: For help using the System Setup program, press <F1> while in the program.
3 Press <Enter> to open the Integrated Devices screen.
4 Choose the option for your integrated network interface controller (NIC).
This option enables or disables the system's integrated NICs. The options are ON without PXE, On with PXE, and Off. The option On with PXE allows the system to boot from the network during every boot. Changes take effect after system reboot.
The PXE boot from the network enables the automation of a number of management tasks, such as the initial configuration of new systems, diagnosis of problems that prevent the operating system from functioning correctly, and configuration updates prior to booting the operating system. These remote operations can lower the costs of system administration and technical support.