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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)

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I believe you're referring to the "temporary" directories left behind by Windows Update for forever after.

These are normally safe to delete. To be absolutely sure, I would first park them in a temporary directory and see if there are any problems across a few reboots or when using Windows Update. If no troubles or funny messages, then they can be deleted with confidence.

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