Wrong read out for RAM ?

Speccy read-out told me that my Notebook has 2 slots with RAM 512MB, DDR2 and 266MHz

After taking them out,m the label shows: "512MB 1RX8 PC2-5300S-555 LF"

Which I found after some research to mean:

PC2-5300 = DDR2-667 => 666 MT/s => 333MHz

So, it’s not 266MHz, PC2-4200 means 266MHz.

It was an expensive mistake, am I a fool to trust Speccy? :angry: