Is it possible to reset NXP LPC2100 microcontroller from code
reemrevnivek has the right idea, but there's a better way.

WDTC = 1024;              // short timeout; we don't care (won't be using it)
WDMOD = WDEN | WDRESET;   // watchdog resets CPU
WDFEED = 0xAA;            // start ...
WDFEED = 0x55;            // ... watchdog.
WDFEED = 0xAA;            // start ...
WDFEED = 0x00;            // ... invalid WDFEED sequence causes instant reset.


That will give you an immediate reset without the need for waiting.

Note that simply jumping to location 0 isn't the same as a real reset. Jumping to 0 doesn't reset any peripherals nor does it reset the ARM core's state. It may sound like I'm nitpicking here, but you can run into some very unusual and difficult to debug issues if you are expecting a reset and don't actually get one.