Defragmenting and not quite enough space left on dirve to do it

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From: saturnin02 (saturnin02_at_hotmail.com)
Date: 11/13/04 

Date: Sat, 13 Nov 2004 15:20:19 -0500

WIN XP HE
Hi,
I want to defrag my C drive but I get the message:
"Not enough space to defrag. Defrag needs 15% to defrag and only 11% is
available. Do you still want to defrag?"
There nothing else I can delete from the drive to create more space.
Can I go ahead with the defrag anyway or will it just not work?
Tx,
S