!!!!!Dont run the engine, you will destroy it!!!!
What make/model/year/mileage is the car and when was it last serviced?
Does the light go out when you rev the engine a little?
The most common causes of low pressure are-
Low oil level (check using dipstick and top up if required).DO NOT OVERFILL.
Poor quality/wrong grade of oil used or oil change overdue (service intervals vary between different engines but if it hasn't been changed in the last year I'd get it done).
Worn engine (usually only on very high mileage engines nowadays)
Faulty oil pump, faulty pressure sensor or choked pick-up pipe in sump (all need to be checked by mechanic/technician).
If the oil level is low, and topping up solves the problem, make sure you check the level every day for a couple of weeks. If the oil is going down fast it may be a sign of other engine problems.
g.robb
April 2009