Congrats Teressa I have a p25 s607 very similar in many ways. Your machine should be fine for digital editing.
Where should I start ... don't worry at all about warranty in doing upgrade to xp pro you can use the recovery dvd that came with your machine and put it back to original install condition if you needed to. Most people though dont have much good to say about compusa warranties if you paid for the 3 year deal from them try to get your money back ( ie threaten to return it maybe or try a line that your company will pay only for the toshiba direct warranty ).
Some people aren't real happy with toshiba service either but its still way better than compusa if you need it especially traveling so far get the toshiba accidental damage 3 yr coverage if you crack your screen for example you will be protected. Toshiba is starting to get real picky though apparently when people spill drinks etc into the laptops keyboard so be careful there cause may claim you voided warranty there.
There's a bunch of exploitable microsoft security holes if you connect to the internet be careful i advice at least downloading free zonealarm from www.zonelabs.com
to have your own firewall and making sure your antivirus protection is up to date.
XP has some really nice features like creating restore points where if you have software install problems you can easily roll back think about getting a good book on xp ... have fun with your new machine it should be way powerful enough to do what you want.
PS If you haven't blown all your money think about getting some kind of external storage (usb hard drive etc) so make sure you have two copies of things critical to you or you can use cdrw disks (rewriteable).