DELL INSPIRON 14 4030

Dear friends,

I have bought new laptop last week. When try to boot my laptop, some time following error is coming. Some times it is booting well and showing windows directly. Some times it is showing error 

“For Atheros PCIE Ethernet Controller... check cable connection

PXE-E63:error while initializing the NIC
PXE-MOF:exiting intel PXE ROM
No bootable device-insert boot disk and press eny key”

 What can I do?  Please help me

System details:

 Windows 7 professional, 4GB RAM, 320GB hard drive, 512 MB Graphic card

- thanks in advance,

-Sasi