Non compatible ram working fine, why?

Hi guys!

I have purchased a laptop for my mom... and i have interchanged the ram between the new and my old one (4gb of ram for my mom is too much and i need it lol).


Here the data:
My laptop:
manufacturer recommends : 533mhz or 667mhz DDR2 SDRAM
And it has installed : x2 1GB 2Rx8 PC2-5300S-555-12

the new laptop:
manufacturer recommends : 800 DDR2 SDRAM
And it has installed : x2 2GB 2Rx8 PC2-6400S-666 12-E1


I have switched the memories; i put the x2 2gb of the new laptop in my old one and my x2 1gb in the new laptop.

So the new configuration is as follow:

My laptop

manufacturer recommends : 533mhz or 667mhz DDR2 SDRAM
And it has installed : x2 2GB 2Rx8 PC2-6400S-666 12-E1

the new laptop:
manufacturer recommends : 800 DDR2 SDRAM
And it has installed : x2 1GB 2Rx8 PC2-5300S-555-12


Everything is working fine but i want to know if there is something i should worry about what i did (despite i still dont know how 800mhz are working in my 533-667mhz system and how the new 800mhz laptop is working with 667mhz ram memory since memories are out of the recommended)


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Thank you for your answer!

ok, i suspected that, and now i ask you; with system downgrading the memory to what is capable to handle... would that cause any problem?

and in the other system, the laptop which is running the memory at 667mhz, would that cause a problem?

Just to save those bucks... but i will take that into consideration