Blue screen STOP:0x0000007E - System disc doesn't work

I have a DELL Inspiron 9400 ( 2007- 17" 1920x1200, 1,83 Ghz, Core TM2 Duo, 100GB, NVIDIA GEFORCE 7900S 256Mb).

I suddeny stopped while listening to music. For about 7 days there had not been any connection to the internet on that moment of crashing. The message on the blue screen:

with accompanying words: STOP:0X0000007E. Something with physical memory dump and I should switch off caching and shadowing in BIOS, but after entering BIOS with F12, it was impossible to change anything of that kind. Of course it was also impossible to update the BIOS ( A09 - 6-27-2007), for nothing reacts.So I tried the safe modus and I tried to start up with the official DELL disc I've got with my Inspiron 9400. It doesn't work. The only thing that happens, is the beginning of a new setup and than it stops after about 8-10 minutes with the same blue screen. At first switching on the laptop I see the Windows screen with coloured lines and dots. F2 and F12 bring me to the BIOS and there is nothing to be done. There is no reaction on giving any command what so ever.

My question is: if I buy new DELL RAM memory ( f.i. 4 x 1GB - 128x64 - 800 MHz ) and I replace the old RAM memory ( 2 GB -533Mhz-DDR2 SDRAM ) shall I be able to start up my system?

Or, would anything else be a better idea.

Thanks for responding in advance.