Transact SQL :: Remove Read Only From A Database?

i have a data base sql Server .I wrote a stored procedure or attach my database but it is attached in read only mode how can remove read-only.

this is my stored procedure.

create procedure attache
as
declare @trouvemdf int
declare @trouveldf int
if exists (select name from sysdatabases where name='Gestion_Parc')

[Code] ....

i try this EXEC sp_dboption 'Gestion_Parc', 'read only', 'FALSE' but it causes those error

Msg 5120, Level 16, State 101, Line 1
Unable to open the physical file "C: Gestion_Parc.mdf". Operating system error 5: "5 (Access is denied.)".
Msg 5120, Level 16, State 101, Line 1
Unable to open the physical file "C: Gestion_Parc_log.ldf". Operating system error 5: "5 (Access is denied.)".
Msg 945, Level 14, State 2, Line 1

[Code] ....