Drive wont read burned dvds

Hi all, my friends burned me 5 dvds of .avi files and when i put the dvd in my drive, it doesnt even register! it asks me to insert a disc when i click on it. on each one theres about 25 170Mb files. is there any software i need to read these? they are dvd+r and they were burned with some sort of nero program, i dont know what tho. anybody know whats wrong?

You might try opening the disks with ISOBuster. There is a free version available for download here: http://www.isobuster.com