Delete hiberfil.sys Hibernate File Windows Vista
My main PC is Windows Vista and I’m getting a bit low on space, I needed to do some editing on a large audio file and during this it creates a massive temp file, and it kept filling my C drive up.  As a temp fix I found a way to temp disable Windows Hibernate mode.  
The hibernate file just saves the state the machine was in when you put it into Hibernate mode, it is safe to delete. 
- Click Start, and then type cmd in the Start      Search box.
- In the search results list, right-click Command      Prompt, and then click Run as Administrator.
- When you are prompted by User Account Control,      click Continue.
- At the command prompt, type powercfg.exe      /hibernate off, and then press Enter. 
- Type exit, and then press Enter to close the      Command Prompt window.
I then deleted the hiberfil.sys file from the root of the C drive, this then gave me an extra 4Gb.  
I did what I needed to do and then repeated the above procedure but this time typed powercfg.exe /hibernate on to re enable the Hibernate mode.