Although you can reboot your Mac OS X into Windows with the System Preferences to change the startup disk or hold Option while you are rebooting, there is an easier way to do it without any hassles. This is done using an AppleScript and the magic of Quicksilver. To do this open AppleScript Editor and copy paste the given below code:
do shell script "bless -mount /Volumes/WINDOWS/ -legacy -setBoot -nextonly" with administrator privileges
do shell script "shutdown -r now" with administrator privileges
# Then save the script file anywhere you want to.
# Open up Quicksilver interface and then the Preferences->Catalog tab; and hit the "+" sign to browse the folder having the script file you just saved.
# Now, you can launch Quicksilver, type-in "reboot" and the reboot script will pop up so that you can reboot into Windows.