NO DISC ERROR

Sounds like a dirty or failed laser or DVD mechanism /drive.

Try a DVD/CD lens cleaner (must say both). If you can, try wet & dry version with alcohol based cleaner - Alsop are a good brand.

If this doesn't work, the drive has likely failed. Its unlikely to be economical to repair - but you could always connect a cheap DVD player to the Sony system - the sony system can then continue to provide surround sound audio, whilst the cheap DVD player plays the discs!

Otherwise - sell the system as separate parts (speakers, remote, cables, DVD player) as someone is bound to be desparate for the speaker set on its own to complete a system and will often pay more!