Microsoft does not provide any clean upgrade path from a 32-bit operating system to a 64-bit version. Basically, you will have to do a clean install. You can simplify the migration process by using System Migration Assistant at http://www-307.ibm.com/pc/support/site.wss/document.do?lndocid=MIGR-50889.
With regards to the boot problem, I have found that certain discs and/or certain optical drives will take longer to initialize which can cause them to be skipped during the boot sequence. To work around this, press F12 during the ThinkPad splash screen until you see "Prepaing Boot Device List" When the boot menu comes up, select the optical drive and hit enter. Sometimes you may need to wait a few seconds before hitting enter in order to allow the optical drive to fully initialize. After hitting enter, the disc's boot loader will start and you'll see "press any key to boot to CD / DVD..."
If that doesn't work, try booting the media on another computer; it's possible the disc is defective (or has some dust on it.
