|The first step is to clean the lens using a cd/dvd cleaner.|
Here in the UK these cleaner kits can be bought for around £1 in a cheapo store.
If that does not work and your pc is a desktop, try your drive in another pc and a known good drive in yours. This will (hopefully) isolate where the problem lies.
If (as I suspect) your drive, they tend to be throwaway items, as it is far cheaper to replace than attempt repair.
Advise back on progress.
Good Luck. Keep us posted.