FINDING, EXAMINING AND DELETING COMPRESSED FILES RESULTING FROM THE DESK CLEANUP SYSTEM TOOL

The desktop is a Dell Optiplex GX260, with Windows XP, Professional Version 2002 and Service Pack 3.

For many years I have been using the System Tool,  Desk Cleanup to compress old files from the C: drive.

I need help to access these compressed files, examine them if i can then delete most if not all of them.

I have assumed that any file that the Desk Cleanup tool has compressed is no longer available or is used by any active programs in the computer. Is this a correct assumption ?

What is the average memory space that one MG of file(s) memory is compressed to ?

Any help and advice would be appreciated.