Hello codahiky, welcome to NST
In addition to moving the cd drive up in the boot sequence you also need to press a key to boot from cd/dvd when it prompts you to. Otherwise, it'll go on to boot from the hard drive.
Are you sure its looping? SP2 for Vista jsut came out within the past 2-3 weeks via WU and requires that the system reboot 1-3 times during installation. Check the stages as well as the percent to see if it'll go onto to the next stage. In addition it'll say to the left of the message "Installing Service Pack". If its doing this let it finish the installation.
In
our wiki you'll find the instructions for startup repair and manual recovery from the recovery disc should you need it. You may need to attempt startup repair 2-3 times to fix everything. Try that first before moving on to manual recovery.