Hello casca and welcome to the PCA Forums.
Check in system to see if there is an exclamation mark against the drive. If there is follow the wizard for troubleshooting tips or post back here and somebody will help you further.
To check the system go to: Start/Settings/Control Panel/System/Device Manager select the drive then Properties. Sorry if this is teaching granny to suck eggs.
Your laser may just need cleaning. You can use a CD cleaning disc to do this.