Hi,
I would suggest you to perform system restore to before a time the issue occurred.
I would also suggest you to check with other DVD disk.
Method 1:
I would also suggest you to check the following services from the steps listed below.
**a.**Open Administrative Tools by clicking the Start button, and then clicking Control Panel. In the search box, type administrative tools, and then click
Administrative Tools.
b. Double-click Services. If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
c. Right-click the Volume Shadow Copy service, and then click Properties.
d. On the General tab, next to Startup type, make sure that Manual is selected.
e. If the service is not already running, under Service status, click Start, and then click OK. If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
f. Now under properties click the Dependencies tab.
Look for the “Dependencies” and make sure all the dependency services are running and set to “Manual” or “Automatic”.
Method 2:
I would suggest you to perform system restore from the recovery option and check.
What are the system recovery options in
Windows Vista?
http://windows.microsoft.com/en-us/windows-vista/what-are-the-system-recovery-options-in-windows-vista
Also refer:
How to back up files and recover data
http://www.microsoft.com/athome/setup/backupdata.aspx
Back up and restore: frequently asked questions
http://windows.microsoft.com/en-us/windows-vista/back-up-and-restore-frequently-asked-questions