1TB 7200rpm drives for ultrabay? jan 2013

[allen]

hi,
every couple years my t60p's ultrabay HDD gets full, and i need to upgrade to a larger one.
the last one is hitachi travelstar 7200rpm 750GB drive.
new egg claims there is 1TB one now available:
http://www.newegg.com/Product/Product.a ... 6822145875

but is hitachi still a company?
do they still make hard drives? or are they part of western digital now?

the western digital website has blue, black, and green laptop drives,
some of which are smaller or larger than 9.5mm.
15mm doesn't fit in ultrabay right?

then there's the seagate momentus laptop, non XT, though the 7200rpm model doesn't seem to be 1TB yet.

do 7200rpm 1TB drives exist?

also,
if the ultrabay drive is all data storage, and the primary drive is the OS and software, does the ultrabay drive get slower when over 75% full? i used to hear that was the case for hard drives. i'm not sure if it still applies.

thanks,