To change the command history settings
Open Command Prompt
Right-click the title bar, and do one of the following:
To change command history settings for all command prompt windows, click Defaults.
To change command history settings for the current command prompt window only, click Properties.
On the Options tab, under Command History, specify a buffer size, and then specify the number of buffers to use.
To open command prompt, click Start, point to All Programs, point to Accessories, and then click Command Prompt.
Changing the buffer size changes the number of commands a buffer can store. Changing the number of buffers changes the number of processes that can have distinct history buffers. Increasing the number or size of buffers uses more memory.
To eliminate the listing of duplicate commands in command history, select the Discard Old Duplicates check box.