Can you give more details?
There is a log file, errors.log--which in older builds of Microsoft
Antispyware, could grow to 4 gigabytes on NTFS partitions. If this is the
case in your machine, stop Microsoft Antispyware, and delete the file.
Quarantine is a folder, typically containing many individual files. If your
quarantine folder contains 4 gigabytes worth of files, I would wonder
whether they were quarantined MP3 files.