Hello,
The Enteries you are looking are the Risk Logs, from where you are trying to delete the Files in the Quarantine.
Here the Enteries would remain as a part of Risk Logs.
Incase, you feel the Quarantine files are piling up.. check this Thread below:
https://www-secure.symantec.com/connect/forums/quarantine-size-too-large
Secondly in your case, the files are cleaned by deletion and not quaratined.
On a Kind Note: As Cameron highlighted you are Infected with W32.Downadup.B Threat, please work on the Plan of Action as given below -
Plan of Action:
1) Make sure ALL Computers are installed with Symantec EP with latest / updated with virus defintions and
2) Install MS08-67 patch download [KB 958644] on ALL computer.
http://www.microsoft.com/technet/security/Bulletin/MS08-067.mspx
3) Install ALL Latest Microsoft Secuirty Patches / Sevice Packs on ALL machines
4) Disable Auto play with GPO
http://support.microsoft.com/kb/953252
5) Disable Scheduled Tasks with GPO
http://support.microsoft.com/kb/310208
6) Enable Security Auditing with GPO
http://support.microsoft.com/kb/300549
7) Scan ALL the machines...
NOTE: *ALL means ALL client machines and server machines (make sure you don't miss any machine)
Inaddition to this, please check the Article provided below and work upon the same.
1) Best Practice for Downadup.B and Additional information on the same.
https://www-secure.symantec.com/connect/articles/best-practice-downadupb-and-additional-information-same
2) Simple steps to protect yourself from the Conficker Worm
http://www.symantec.com/docs/TECH93179
3) What is Risk Tracer? http://www.symantec.com/docs/TECH102539
Hope that helps!!