I recently noticed on some computers (it seems to affect both Vista and XP), that sometimes one or more folders will appear straight under C:, and have a random name… something like:

c:1ad29fe78456acc5b26351428709

The only pattern I can see is:

there are between 18 and 28 characters in the folder name, the name is only made of hex characters (ie numbers 0 to 9, and the letters a,b,c,d,e,f).

Looking closely at the contents, and I can see that the files seem to belong to a microsoft update that most likely crashed before the folder structure could be cleaned up (I still don’t understand why subsequent updates cannot tidy up after prior failed ones… how hard can it be?).

Anyway, if you notice that a strange folder name with 18 to 28 characters, that has been “hanging around” for a few weeks, then its probably safe to delete it.