You can go into a dos command window (start -> run -> cmd), then type "bootcfg /list". That will list all of the OS's currently configured to boot. If you can distinguish which one is the one you want, you can type "bootcfg /default" and set the default to boot to.
If you know how to remove the read only flag on the boot.ini file, you can do that and then just edit it with Notepad, then save it, and put back the read only flag.
-d