This may be helpful:
Clean, Quarantine, or Delete?
Remove & Isolate suspicious files, Quarantine Files | Internet Security Help
You really need to know what it is and what it may have done as Fooze said. It seems logical that if quarantining these items hasn't had a negative impact then deleting them would be safe. They are very likely either false positives or items that can be safely deleted... toolbars etc .