Problem:
The file "hiberfill.sys" is too big.
Solution:
A. Disable Hibernate (and Delete hiberfil.sys) in Windows 7 or Vista
You will need to open an administrator mode command prompt
by right-clicking on the command prompt in the start menu,
and then choosing Run as Administrator.
Once you’re there, type in the following command:
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powercfg -h off
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You should immediately notice that the Hibernate option is gone
from the Shut down menu.
And also notice that the file is gone.
B. Disabling Hibernate Mode in Windows XP
Go to "Control Panel > Performance and Maintenance > Power Options"
and then find the Hibernate tab.
Source:
http://www.howtogeek.com/howto/15140/what-is-hiberfil.sys-and-how-do-i-delete-it/