Start up disk is full, how do I use my external drive

Hi,
I have on my start up disk..
Capacity: 465.44 GB
Available 108.4 MB

I keep getting a message that my start up disk is full. This started after I tried backing up my iphoto library onto my external drive.

I know I have movies on my hard drive that I do not want to erase (to use later) I would like to put them on the external drive. My question is how do I move these onto the external drive. Do I just drag them over and when I need them just drag them back? Can I use them from that drive?

A while ago I copied all of my 2006 iphoto pictures onto a DVD and I hated doing that because now I have to look them up instead of having them conveniently on my iphoto library.

Thanks!!

assuming they are nit in iTunes then copy those movies over, delete them from your mac and you will be able to watch them anytime from the external

I would keep at east 50 Gig free on that drive just to let the system breath

You can move your iPhoto and iTunes libraries to your external and use them from there. See: http://support.apple.com/kb/HT1229 and http://support.apple.com/kb/HT1449