I just posted an article with simple time value of money routines for the HP15C. (I've also ported these to my wife's HP11C and the HP33S.) While not as fancy as the program in the HP-15C Advanced Functions Handbook, they only take up 23 program steps, three labels, and two memory registers. Combine this program with the equation for compounded interest (PVF = (1+r)^N ) and the adjustment to the present value annuity factor when payments are made at the beginning of the month ( PVAFbeginning = PVAFend(1+r} ) and you can handle the book examples.
Edited: 16 Sept 2011, 1:14 p.m. after one or more responses were posted