Example Delete all files with starting with blah in Folder “FolderName” older than 30 days.

forfiles -p C:\FolderName -m blah*.* /d -30 -c "cmd /c del @path"

Newer Windows use slightly different parameters - e.g. Windows 2012

forfiles /P "C:\Users\remoteeir\Desktop\PingTest" /M PingTestResults_*.* /D -3 /C "cmd /c del @path"