installing windows xp pro shouldn't be a problem, i've done it twice now on two different computers without a single hitch. and besides, if anything does manage to go wrong, i still have that big stack of recovery cds that sony gives me.
linux doesn't seem like it'll be too hard, i was looking at a couple of sites and there seem to be many users with success with vaios and linux. most people seem to have trouble only with using the included modem of the laptop, but since i'm never going to have to use dialup again, that's not an issue.
you can goto this page for a success story:
http://www.shallowsky.com/vaiolinux.html
it's about a lower model number than we have, by around a year or two by now, but it should still apply. sony uses most of the same hardware in this one.
oh yeah, i guess i already have used some linux on that box, as i got warlinux for it. it works except for the fact that i don't have a prism card.
*oh yeah, go check out wardriving.com for that one if you got prism, cos i ran into somebody who couldn't use netstumbler. it's contained in a 100% bootable iso that worked fine, except for the not having a prism card part. heh. second note: just talked to him again, it didn't work right. go figure. but it might work for you.*