Windows 7 keeps on writing thousands of jpg files on c:\windows\serviceprofiles\networkservice\appdata\local\microsoft\media player\art cache\localmls subdirectory as system files.
This same issue caused my anti-virus program to take over 20 hours to run its complete system scan. I found over 871,000 art cache files that look to come from browsing amazon.com's music store.
I deleted the art cache files by deleting the windows\serviceprofiles\networkservice\appdata\local\microsoft\media player\art cache\localmls folder and creating a new folder witht the same name. To prevent the folder from filling up again with art, I disabled the Windows Media Player network sharing service using the procedure described in this link:http://www.mydigitallife.info/2010/01/27/how-to-disable-windows-7-media-player-network-sharing-service-wmpnetwk/.
Now my slow scan probelm is gone. It took only 3 hours, 15 minutes to run a scan of 750GB internal drive and a 500GB external drive.
"Turning off the "Windows Media Player Network Sharing Service" has seemed to stop it... for now =)"
Missing Hard Drive Space (windows 7)
Alternatively perhaps you create a batch file to run at Startup or by Schedule Tasks to delete *.jpg files that appear in that folder?
A rough example of a batch file would be along these lines. It would be created in NotePad but saved as a .bat file.
cd "windows\serviceprofiles\networkservice\appdata\local\microsoft\media player\art cache\localmls"
That is only a rough guide and may need plenty of amendments by you as I am not that familiar with batch files but it should not be too hard to do. The batch file when run manually or in Scheduled Tasks would need Administrator privileges or the access permissions of localmls set suitably for the user.