Hello i have dell 5520 with in warranty and after using couple of months i have issue this product is covered by one or more of the following patents ... and i read some forums and i update all driver bios but it didn't stop  then i disable boot from network and it start working properly for few days around one week but now it give me beep and on running windows and then system hang and when i restart and it say no boot device found . and no harddisk is showing in boot options but after some time when i start again it works fine for some time then same issue over and over again . please guide me as soon as possible