How can I configure my pagefile size to be “system managed” for Windows XP and later versions?

You can specify pagefile location and size by modifying the PagingFiles value under the HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerMemory Management registry subkey. If you want the system to manage pagefile size, simply set the initial and maximum pagefile sizes to 0, as the following example shows:

C:pagefile.sys 0 0
You must reboot the machine for the change to take effect.