This article was released a couple of days ago and can be good to know about.

From the MS KB:

“A PXE enabled Distribution Point will generate a number of files under C:\ProgramData\Microsoft\Crypto\RSA\S-1-5-18 for each PXE request that it services on the network. This occurs whether the device sending the PXE request has a Task Sequence deployed to it or not. The generation of files will continue and may consume available hard disk space.”

For more information see the whole article: http://support.microsoft.com/kb/2713467