I have 40gb hdd.need a partition scheme for

Using the Windows XP installation disk, procede to install windows normally. In the windows setup you will get a list of options. Choose "C" to create partition. Create a 20GB partition. When that is done create another 20GB partition unless you plan on installing another Operating System such as Windows 7 later. If you want to keep XP and install Windows 7 at a later date on the same PC, then Set up 2 - 10GB partitions for Operating Systems and 1 - 20GB partitions for games. Make sure to install the games on the 20GB drive letter only so that Windows has enough space to run.