how to use a laptop as a hard drive

Hi,

I was recently at a one-on-one session and switched my pictures from my old apple laptop to my new iMac. My laptop is old, but I was told that I can still use it as a hard drive by pressing the letter "t" at startup which puts it in target mode. I also need a firewire with an adapter to transfer items to my iMac. I recently purchased software that requires you use a disc for installation with a DVD drive. I do not have a disk drive on my iMac. Can I use the laptop's driver and the laptop as a hard drive and load that software on my iMac. If so, how?

Thanks!