32bit to 64 bit on any Windows OS requires a clean installation. You should be able to do it with an upgrade disc though.   "will the other disks that come with a Dell computer then be used to install the original software on the laptop"   Possibly, but you can register your system at the link below, then download your pre-installed software if the system qualifies.   [URL]   .  
Dell indicates the Inspiron 1545 supports 32 bit and 64 bit Windows 7. My 1545 has 32 bit Vista on it. I would like to upgrade to 64 bit Windows 7.   Will an Upgrade disk work, or will a new installation 64 bit Windows 7 disk be needed ?   If the latter, will the other disks that come with a Dell computer then be used to install the original software on the laptop, or will separate disks, or downloads, be required ?
32 bit Vista to 64 bit Windows 7