求助电脑硬盘问题，多谢了！

I have a notebook running Windows XP Pro with 20GB
hard drive. Today I can not save any PDF file under
"My Document" folder. The error message shows:

--The disk you were saving to or the disk used for
temporary file is full. Free some space on this
disk and try again

I checked the disk property, and found I only used
5 GB totally.Still 15 GB available. I went to
"Tools"-->"Option" and cleaned temp internet file,
but still can not save any PDF file to that folder.

Anyone know how to slove this problem? Thanks a million!