your computer will not boot from a service pack disk, only from a operating system disk, if you mean that you have a disk that has vista WITH sp1 then yes it can, you will need to to modify your boot settings making your cd/dvd drive the 1st boot device.
when you first turn you pc on, it will usually say something like "Press F12 to access boot menu" (or something similar)
you need to set it to boot to the DVD/CD drive first.
Also entering the BIOS will lead to this result too. Again, it will tell you at startup what to hit to access the BIOS. Like, on my PC i have to hit 'del' to open the BIOS.