Issue Database 'xxx' cannot be opened. It has been marked SUSPECT by recovery

Follow below mentioned steps to solve the issue.

Step 1: Stop sql services
Step 2: Open this path C:\Program Files\Microsoft SQL Server\MSSQL10_50.SQLEXPRESS\MSSQL\Template Data

 and copy MSDBLog and MSDBData files from this folder and paste it to
C:\Program Files\Microsoft SQL Server\MSSQL10_50.SQLEXPRESS\MSSQL\DATA folder (confirm replace).

Step 3: Restart the SQL services.

Then u can use it .