It's usually caused by registry cleaners that remove the ignore low space on drive D setting. Google this!!!
How to ignore windows low disk space?
As to the shutdown, please clean your laptop. Here's the links:
Running Vista , bottom right icon keeps saying "D" drive is nearing capacity.
I run Norton and PC matic, do defrags, scans, empty temp internet files and recycle bin.
Is the "D" drive issue causing the shutdown, or Windows Vista ?
is the PC Matic program any good? Or was that $50. up in smoke ? it did seem to help in some areas, but I still have the sporadic shutdowns ...thnx