When it quarantines something it encrypts it, so it is still on your hard drive albeit disabled.
You can remove it by opening SecurityCenter (right-click or double click the taskbar icon)
2009 products... click Advanced view bottom left
Click Restore left
Click Files right (going frommemory, sorry if I missed a step)
Remove the files from there.
Click Navigation at top right
Click Quarantined and Trusted Items (below)
You can remove them from the various sections there. (Click to expand)
Just noticed your other question, sorry. It's late and I am tired.
Boot to Safe Mode (tap F8 repeatedly while booting up)
Go to your hard drive in Computer (My Computer in XP)
Right-click it and select Scan.
See if anything else is detected.
You may still have some spyware onboard in which case try one of the tools listed here.