Generally I would go for Crucial RAM on Dell systems. We find that they sometimes don't always accept RAM from other vendors. In this case Crucial have 1.35V modules: [URL] They also have PC3-12800 modules which will be the fastest. You might also want to consider a SSD also however the high capacity ones are still quite expensive. This hidden legacy driver, I'm not sure. Looking around it seems related with the Dell Reader: [URL]  [URL]
I recently went from 32bit to 64bit Windows 7 Pro following the "unofficial" Reinstallation Wiki (the second time around) to the letter.  Here what's happening:  bouhgt two 4GB sticks of DDR3 1600 MHz 1.5 volt RAM.  It is fully recognized in BIOS rev. A16. 3.8 GB is usable and works in Windows 32 Bit perfectly.  When I attemt to load Windows in 64 Bit I get 1) White Screen to Windows Repair loop -both DIMM A & B loaded 2-BSOD when either stick is loaded in DIMM A only. Is the voltage incorrect?  Why do these modules work perfectly in 32 bit?  Should I exchange for 1333 MHz at 1.35 volts?  Please advise
32bit to 64bit upgrade RAM problems