I had this problem in my 2.33 c2d MBP too.
boot up XP in parallels, and change the boot.ini timeout to 10 rather than the -1 that it is. this is in system properties\advanced tab\startup and recovery settings.
also change the timeout for the profiles selector to 10. this is under system properties\hardware tab\hardware profiles.
make sure for both that your default profile/choice is the default (bootcamp) config. when it loads into bootcamp u will get full functionality. whenever you boot into parallels, make sure u select the parallels option both times.