Is there such a thing as high density PC100?

[beatle]

I bought a 256 meg stick of PC100 from 11cb.com for my girlfriend's HP Omnibook 6000. Since it has a P3-650, it needs PC100 memory. Her laptop takes up to 512 megs (2x256). I was under the impression that all PC100 memory was low density, thus there should be no problem. It arrived at her house today and she installed it, booted, and it showed 192 (she already has a 64 meg stick). This looks like they sent her high density ram, which is half useless. Is this possible? If there is such a thing as high density PC100 (and that's what this is) then who can I buy LOW density PC100 from that won't cost me an arm and a leg?