Too many minidumps
By default Windows 7 now keeps the last 50 minidump files (memory images saved when your PC crashes). If you're keen on using dump files to troubleshoot crashes then this is good news, but if you've no interest in that kind of advanced debugging then minidumps are just a waste of your valuable hard drive space. In which case you should run REGEDIT, browse to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\CrashControl, and set MiniDumpsCount to 1. Windows will only now keep the last dump file and you'll free up a little hard drive space.