Cannot Open Backup Device

DEAR ALL, I RUN THIS CODE FROM SQL QUERY ANALYSER FOR SQL EXPRESS

USE CPHONE

GO

BACKUP DATABASE CPHONE

TO DISK = 'C:CPHONE.Bak'

WITH FORMAT,

NAME = 'Full Backup of CPHONE'

GO

-- Optionally, create a logical backup device,

-- AdventureWorks_Backup, for this backup file:

USE master

EXEC sp_addumpdevice 'disk', 'CPHONE_Backup',

'C:CPHONE.Bak'



I RUN EITHER LOCALLY OR FROM ANALYSER OF OTHER PC

AND THEN I TOOK THIS ERROR


Msg 3201, Level 16, State 1, Line 1

Cannot open backup device 'C:CPHONE.Bak'. Operating system error 5(error not found).

Msg 3013, Level 16, State 1, Line 1

BACKUP DATABASE is terminating abnormally.


ANY IDEAS PLS ??