Help! Strange "fff" files in Windows ME!

Hello. I've just upgraded to Windows ME, and have carried on my
practice of tidying up all dubious-looking files at the end of each
day, i.e. when I search for "all files created in the last 1 day",
anything that looks to be of a temporary nature gets deleted. I've
noticed a whole load of files are created in C:\WINDOWS every day.
They are all ".tmp" files and all have long names beginning with
"fff", eg:-

fffbc343_{581A50.....
fffe0c27_{CA29F3.....
fffe28a5_{8A05C0.....

Can anyone tell me what application might be creating them, and why?
There are dozens already, and even though they are of neglible size,
I'm scared the volume of them will create directory problems soon.

Thanks in advance for any pointers.
Adrian Willis.