Right Click on My computer and select Properties. Click the Advanced tab then Settings in Startup and Recovery.
In system startup it will allow you to set the default operating sytem that is loaded - set this to Windows XP Professional, then set the Time to display list of Operating Systems to, say, 5 seconds.
This gives you a chance to do something at the boot menu if you actually want to, but isn't too long that you fall asleep waiting for XP to start loading.
This way, it will showthe boot menu for 5 seconds, then continue loading XP.
Hope this helps.
Alan