There are number of BOOT.INI switches that are useful for driver developers that wish to test their drivers under a variety of different system configurations without having to have a separate machine for every one. For example, limiting the amount of memory NT sees can be useful for stressing memory loads, and limiting the number of processors for testing scalability. I’ve compiled a complete list of the options that BOOT.INI currently supports. This list is reproduced in the Startup, Shutdown and Crashes chapter of Windows Internals, where you’ll find more information about the boot process. Entries in red were introduced in Windows 2000 and those in blue introduced in Windows XP or Windows Server 2003.

Note: to see what options I system has booted with examine HKLM\System\CurrentControlSet\Control\SystemStartOptions.

http://www.sysinternals.com/Information/bootini.html