user defined type as a primary key

[umeshpotdar]

hi frdz
i have created user defined types in sql server 2005
i want to use these types as a primary key in my table
but i got error when i assign primary key to it
(error ----- Primary key can not be exceed 900 bytes)
so what should i do for that
i must have to use it
so can anybody tell me
plz. ........