W2003 Large (14GB) System Volume Information Dir, Suspect Shadow Copy

My Windows 2003 SBS Premium server has a System Volume Information dir that is 14 GB, my entire system is 31 GB. In the dir I see files with the following gobbly-gook nameing:

{77ec9463-f15f-11da-a34a-000ea6311b35}{3808876b-c176-4e48-b7ae-04046e6cc752}

The largest of them (~1.6 GB each) are created at the time my nightly backup runs, at 2:00 AM. The event viewer shows NTBackup and shadow copy starting and stopping at that time. All messages are info and look normal; no warnings or errors.

The stream contains 2 ntbackup commands. One backups up the system state and some user directories. The other backups up Exchange data.

My questions are:

What are these files?
Can I delete them via Windows Explorer? By another method?
How do I stop them from coming back?

I thought Shadow copy was a protocol to tell applications to "get out of your files for a minute while backup backs them up". Is there more to shadow copy than that? If so, any articles you can recommend that explains Shadow copy would be appricieated.

Thanks in advance.