Unable to delete unwanted files: There is not enough free disk space

Hi,
I am having error of low disk space on my computer. I then tried to delete unnecessary file from a computer, but I am very astonished to look at this error given to me by my computer who was complaining of low disk space already.
When I try to delete file it says:

Error Deleting File
Cannot delete DOCPROP: There is not enough free disk space
Delete one or more file to free disk space, and then try again.
Now I cannot understand why it requires free space to delete a file. If I have space, why should I delete the file?
I am not deleting files due to the space issue.
Anyway, Microsoft is so unexpected kind of company understanding of which the holy error are ahead of my mind, so please guide me in understanding this error.
Thanks.
