System Restore - Shadow Copy Storage space in vista

Listing shadowstorage in command prompt:

The shadow copy storage area is where all types shadow copies are stored on each volume where VSC (Volume Shadow Copy) is turned on.

View shadowstorage using "vssadmin" command in command prompt. But it can't be viewed in normal command line.
To use vssadmin command, you have to run command prompt as an Adminstrator.

For more details about how to run command line as an adminstrator, view How to run as Administrator using Command Prompt?

In command line, type
C:windowssystem32>vssadmin list shadowstorage

It displays all shadow copy storage associations on the system and their size:
vssadmin 1.1 - Volume Shadow Copy Service administrative command-line tool
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Shadow Copy Storage association
For volume: (D?Volume{a3930ad7-3f30-11de-864b-806e6f6e6963}
Shadow Copy Storage volume: (D?Volume{a3930ad7-3f30-11de-864b-806e6f6e69
63}
Used Shadow Copy Storage space: 411.281 MB
Allocated Shadow Copy Storage space: 700 MB
Maximum Shadow Copy Storage space: 762.449 MB

Cleanup the disk if shadowstorage occupies more space.