Understanding Timers, Counters and Prescaler Registers on the STM32
If you just set the period register to 1, this won't automatically enable interrupt generation. You will need to do 2 additional steps:


Enable the 'update' interrupt for your timer using the TIM_ITConfig() function.
Enable the timer interrupt source in the interrupt controller by calling NVIC_Init() with appropriate parameters.


Of course, you should not forget to enable clocking of your timer peripheral using the APB1PeriphClockCmd().

There's a detailed example on configuring timers on STM32F4-Discovery here: http://visualgdb.com/tutorials/arm/stm32/timers/

STM32VL-Discovery is a bit different, however the main steps are the same.