It's usually somewhere in the region of 150 minutes (2 hours 30 minutes) if you're talking about making a 'movie' DVD.
Clearly more can be 'stored' if the footage were to be in a compressed format (MPEG, MOV, etc.).
-------------------- TFC 'Going to trial with a lawyer who considers your whole life-style a Crime in Progress is not a happy prospect.' - Hunter S Thompson (1937-2005)
45 minutes shouldn't be a problem using a DVD authoring/burning app (Nero, WMM, etc.) even though the AVI file itself could be much bigger depending on resolution/bitrate - i.e. 25 frames per minute (full frame 4:3 video) starts at about 0.5Gb per minute.
-------------------- TFC 'Going to trial with a lawyer who considers your whole life-style a Crime in Progress is not a happy prospect.' - Hunter S Thompson (1937-2005)