M1710 667mhz Or 800mhz Ram

Hey ppl long time no post been away

Anyway installing World of conflict the other day on my M1710 T7600G A07 bios half way though the install i recieved the Blue dead screen crash errr.

After a few tests and error messages for eg

PFN_LIST_CORRUPT

PAGE_FAULT_IN_MONPAGED_AREA

IRQL_NOT_LESS_OR_EQUAL

i decided to run a memory test program since all these errors pointed to memory bad failed etc

After running the memory test it failed on WMATS+ have no idea what WMATS is but i'm guessing my memory has died.

2 questions

Is it normal for memory just to die like this?

And now knowing my memory is crap can i upgrade from the normal 667mhz pc5400 to a more mhz ram like the pc6400 800mhz will my Dell except this up in mhz ram?

Many thanks

P.S oh these are the 2 ram modules i'm currently looking at
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G.SKILL - G.Skill 2GB (PC2-5300) DDR2 667 CL5 SO-DIMM Single Channel
Specification
Capacity 2GB (2GB x 1)
Speed 667MHz DDR2 (PC2-5300)
CAS Latency CL5
Test Voltage 1.8 Volts
PCB 6 Layers PCB
Registered/Unbuffered Unbuffered
Error Checking Non-ECC
Type 200-pin SO-DIMM
Warranty Lifetime
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Samsungl 2GB (PC2-6400) DDR2 800 SO-DIMM Dual in line memory
Specification
Capacity 2GB (2GB x 1)
Speed 800MHz DDR2 (PC2-6400)
CAS Latency ? not known
Test Voltage 1.8 Volts
Registered/Unbuffered Unbuffered
Non-ECC
Type 200-pin SO-DIMM
Warranty Lifetime