Poor service from Dell

Hi all I am not sure if this is the right forum but I would like to post my recent experience of Dell Support regarding a purchase of Inspriron 17R 5720 which having bought 2 x different model Vostro's and had no trouble has rather disappionted me to the extent of not buying from Dell again.  If anyone can answer the points below or had a similar problem I would be grateful.

 Upon first boot and log on an attempt was made to create a set of recovery disks which failed due to faulty image or hardware.

There were dead pixel’s on the screen which was replaced by an authorised Dell Engineer

The machine would run for various periods of time then then go black screen necessitating a hard shutdown.

Upon reboot the machine would give three short beeps before loading as time went on this changed to three short beeps followed by four.

Dell diagnostics run at switch on showed no faults but the Nvidia graphics had disappeared.

Upgrading the Bios as recommended by Dell to version A14 restored the Nvidia graphics.

The machine continued to randomly go black screen and a new motherboard was fitted by the same engineer.

The machine was left in a state of not being able to boot after the engineer phoned Dell.

Following various calls to Dell support, and being deliberately cut off several times there was no outcome.  The Bios was flashed from version A12 to A14 this installed the Windows Boot Manager which allowed the machine to boot, however the Nvidia graphics was not found when running Bios diagnostics or Windows Device Manager. This suggests that the Bios is faulty or the wrong motherboard was fitted.

Following a vast amount of research on the internet it is apparent that Dell has serious issues with this range of machines and has failed to rectify them.

Included in the purchase of this machine is a cost for the Microsoft operating system lic ence which is not supplied but written to the Bios which means that when I tried to reload from a legal retail version of Windows there is no activation code supplied that I can enter.  I believe that this is an nfringement of Trading Standards and will be seeking their advice on the matter. Will post further when I have an answer