Identification
A PS2 format disk simply means a disk that is compatible with a Playstation 2, which is usually a Playstation 2 game. These disks will feature the Playstation 2 logo on the bottom and usually have a silver backing that contains the data.
Blue Disks
Early PS2 games were burned on blue-bottomed disks. The functioning of these games was often problematic, and at times they didn't work at all. Often, the "format disk" message will appear. In such a case, call the game's manufacturer to ask for a replacement.
DVD Disks
While most DVD disks are PS2 compatible, some disks, such as burned DVD movies, may not play in a PS2 and the error message will appear. Look for DVD cases with a "PS2 Compatible" sticker on them.
Scratched Disks
If a PS2 disk is scratched and it takes a while for the system to read it, the format error message may appear. In most cases cleaning the disk using a disk cleaner will restore its functionality.
PS1 Disks
Original Playstation disks can be played in a PS2, but if the PS2 is used and old, the disk format error may appear. Use a laser lens cleaner to clean the lens and try the disk again.