That all depends on the size of all the data on your computer,
The speed at which you can transmit data,
The speed at which your lightscribe drive can recieve data...
For example:- If your total amount of data was 100 Gigabytes and your transfer speed was 500 Megabytes per second then it would take 3.3 minutes.
If your transfer speed was 1 Gigabyte per second it would take 100 seconds or 1.6 minutes...
So..
first check your total Gigabytes and divide that by your transfer speed in seconds, divide that answer by 60 to get minutes etc.
ah..take into account burning speed if you're saving to DVD...