Cannot open backup device 'c:\Program Files\Microsoft SQL Server\MSSQL10.SQLEXPRESS\MSSQL\Backup\ C:\HostingSpaces\dbname_jun14_2010_new.bak'
The error is quite self-explanatory. The file C:\program files\...\Backup \c:\Hosting...\
is incorrectly formatted. This is quite obvious if you inspect the file name. Perhaps ommit the extra space in your backup statement?
BACKUP DATABASE go4sharepoint_1384_8481
TO DISK='C:\HostingSpaces\dbname_jun14_2010_new.bak' with FORMAT
Note there is no space between '
and C: