I noticed a bunch of folders in the root of my hard drive named with a string of hex digits that contain files named with a GUID ending with "mpasdlta.vdm" and "mpavdlta.vdm". From some Googling, I've determined that these files are spyware and virus definition files used by Microsoft Security Essentials. Are these files safe to delete?
(Why doesn't Microsoft follow their own guidelines and store application data in the folders intended for that purpose? grumble grumble)