Blender wont let me save or pack texture

Anyone else get this problem.
I have 4 gigs space on harddrive but when i try save a texture (27meg) it says no space available and cant even pack the image.Despite the fact i was able to save the image just a minute ago then applied some new textures and now it wont save the base texture size has not changed makes no sense

without knowing WHAT your UNKNOWN operating system is
nor knowing what size this “drive” is
nor WHAT the drive is
usb thumb?
flash card?

Nor what format it is in
( fat16 fat32, ntfs,nxfs, hfs hfs2 btfs,ext4 ,…)

there is no way to know

most OS’s and File Systems keep 5% back for EMERGENCY use such as a full drive