Do Windows 2000 or later DHCP clients renew their existing lease on restart?

Start the registry editor (regedit.exe).

Navigate to the HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParametersInterfaces\{

Start the Microsoft Management Console (MMC) DHCP snap-in (Start, Programs, Administrative Tools, DHCP).

Expand the DHCP server.

Open the scope whose options you wish to modify. Select Scope Options, and click the Advanced tab.

Select Microsoft Options from the Vendor class drop-down menu and select Default User Class from the User class drop-down menu. Under Available Options, select the "002 Microsoft Release DHCP Lease on Shutdown Options" check box, as the figure shows. Set its value to one of these options:
1 = DHCP clients send a DHCPRelease message on proper shutdown, which means they'll give up their lease.
0 = DHCP clients don't send a DHCPRelease message on proper shutdown, which means that when the clients restart they'll attempt to renew their existing lease.