Yes of course; just like you can read anything on a DVD/CD drive when a disk is inserted, or any other peripheral device, like another HDD, or PEN/THUMB drive via a USB port; anything basically that is physically connected and supported by the OP sys and MB.
Just a word of caution: if you take out the hype surrounding 'Vista' you will find there could still be issues/bugs etc with it, even upon official retail release this month, so I would still keep XP as my primary 'Operating System for at least another 6 months, preferably a year! Microsoft is well known for using the public for ongoing 'Beta testing' even after RC's 1 & 2 they will still rely on us to deliver-up the bugs to them! Because of this, (regardless what the media/press say, including MS) I would hold-off until the end of this year. You will also find their price structuring will change with time to our benefit, plus you do not have to become an 'inadvertant bug tester' for them, but of course that is up to you.
Hope this helps, and have fun!
I never think of the future, it comes soon enough - Albert Einstein