With the kind of specs you have in your system and to make sure that your system will have an ample wattage supply as the capacitors of the psu ages due to many years of use, you'll need at least 500 watt psu. Since your tight on budget, these might interest you.
Nice thanks! what one you recommend for my computer? and for the graphics card can you link me some?? and will those fit? also does power supply improve performance? thanks a bunch i had no idea of what to buy
But unless you have a 30" monitor, why did you buy a 2 GB card? I think a better decision would have been to buy an 896 MB card and put the rest toward a better PSU. Unless you find a great deal on sale, I do not think you will find what I would call an adequate PSU for $50.
If you are willing to go to $60 - $80 you have lot of good choices: Antec, Corsair, Seasonic.