a lot of that space (if not all if it) is ur "hiber.sys" and "paging" files. lets do an experiment. disable hibernation and disable the paging file temporarily. dont worry, it wont hurt anything, just reverse the process after we've had our experiment.

to disable hibernation follow the instructions in the "Let Me Fix it Myself" section: http://support.microsoft.com/kb/920730

now disable the paging file:

1. click the start menu
   
2. right-click "computer" and select "properties"
   
3. click "advanced system settings"
   
4. in the "advanced tab" under the "performance" section click "settings"
   
5. click the "advanced" tab
   
6. under "virtual memory" click "change..."
   
7. untick the box next to "automatically manage paging file size for all drives"
   
8. select "no paging file"
   
9. click "set" and confirm "yes"
   
10. then click "ok" then "apply" then "ok" again
    
11. reboot your computer
    

after you've disabled both of these run ur experiment again