can I install pc window game into usb external 3.5 hdd and play through it ?

will it decrease game speed or anything ?

my internal hdd full liao

one more question

WD caviar green 160GB with 20% free space
VS
WD caviar black 1TB with 20% free space

which one will perform better with low-end gaming rig,playing latest modern game
I heard people said high capacity hdd will slowdown pc system,especialy with lot of file/document/program

another

thank you so much for all replied

now I'm just gonna buy WD 160GB as my second internal hdd
WD caviar black 1TB it's too big and useless for me because I already have WD MyBook Essential 640GB using as storage for files and documents,and still have 40% free space
all I need just a little bit space for gaming purpose

dont have esata,only usb
playing game feel abit slow,sometime lag

sumore the files in it very important
using it for long time can cause a lot trouble (crash,virus etc)
I'm try to play safe

singapore...just send it via post...call or send email first for confirmation