i am having a macbook white with mac os snow leopard and 2.4 core 2 Duo and 2 GB of memory type DDR3 and i tried to update to mac os lion but the macbook became too slow so i downgraded to snow leopard so would upgrading the memory to 4 GB help
It will help a bit. 2GB is the bare minimum for Lion and Mountain Lion - even 4GB may not be enough if you do much more than the basics.
Personally I'd stick with Snow Leopard but upgrade the RAM anyway, unless you have a compelling reason to use Lion.
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