Dell e 521 adding 2-1 gb of memory will this work?

[willy ray]

Hello,
i have 2 memory sticks for my dell e 521.first one seral no.kvr667d2/1gr. the other one. seral no.kvr533/d2n4/1g. will this work as a pair?

 

[aford10]

They have different speeds and timings. They may work together, but the DDR2 667 will downclock to 533. You may even need to adjust the timings and voltages in the BIOS.