No, the selection is in a file called boot.ini which is a hidden file on the systemroot directory usually c:\
This file will contain something like this
[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(2)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /NoExecute=OptIn
multi(0)disk(0)rdisk(0)partition(3)\WINDOWS="Microsoft Windows XP Home" /fastdetect /NoExecute=OptIn
To change the default OS that loads, change the default= to match the desired OS, if you want it to boot straight away to this OS without any selection prompt, set the timeout to zero.
CARE. DO NOT change any of the multi(0)disk(0) etc statements or your machine won't boot. You'll need admin priviledges to change this, and you may need to remove the read only, system, and hidden attributes. This can be achieved from the command prompt.
type
c:
cd \
attrib -r -a -s -h boot.ini
c:\notepad c:\boot.ini
make the appropriate changes, and save the file. Exit notepad.
back in the command prompt type
attrib +r +a +s +h boot.ini
exit.
Good luck, exercise care!!