I am getting the error message from the title:
The following boot-start or system-start driver(s) failed to load: cdrom
in event viewer during startup, and as a consequence Windows 7 doesn't recognize my cdrom. How can I fix it?
Microsoft says that for Windows 7 that the Hardware and Devices troubleshooter will fix it, but you might try the Win-XP steps (they worked for me):
Note: If the failure occurred after installing (or attempting to) some malware like iTunes, AnyDVD, etc.; editing the key to just remove the corresponding entry (if you can tell which it is) may save you from having to reinstall your other software that makes heavy use of the drive.
The entry for iTunes is typically
Sometimes you can see the last good values at:
LowerFilters keys. The note, from step 3, about last good entries, applies.
Restart the computer.
You may need to reinstall programs like iTunes, Nero, Roxio Creator, DVDFab, etc., to get them to use the drive again.
Note these steps also work for the Event log entry:
The following boot-start or system-start driver(s) failed to load: Imapi