your post is a little confusing
if you want a motherboard to suit lga775 search for that ,
i think what you are refering to is the size of the motherboard that holds the lga775 cpu and that is called the motherboards form factor.
lga 775 fits in quite a few different form factors , ita , micro atx , eatx etc
find out what form factor your board is then you will know if a case supports that size/form factor motherboard