If I have to get a professional, how much do you guys think it would cost??
First time home owner, so I guess I'll be learning this real quick.
If the boxes are not grounded, make sure the first outlet on the circuit is a GFCI. Then wire the line and load sides correctly.
This isn't just a whim. If you don't care about your safety, at least do it for the safety of your children.
The adapters you mentioned are called "cheaters" and should only be used if the electrical box is grounded. However if the box is grounded it is easy and safe to install a three prong receptacle.
Checking for a ground is easily done with a circut tester. If you have little or no electrical experience I highly recommend the Black & Decker Home Improvement book series. They have a basic and an advanced book on electrical repairs and residential wiring. The books are easy to follow and have step-by-step directions. I have found them to be very helpful.
If the electrical box is grounded you should run a bare copper wire from the grounding screw on the new receptacle (3 prong) to a grounding screw inside the electrical box as Bob suggested. This wire would only need to be approximately 4 to 5 inches and does not require you to run a wire behind the walls.
Bob is also correct in advising you to install a GFCI receptacle if the electrical box is not grounded. With no grounding wire these receptacles will not necessarily prevent damage to your appliances and electronic equipment but will protect you and your family in the event of a short circut.
I hope this information helps and good luck with the repair.
The boxes we are talking about are the little boxes that hold the outlets, not the fuse box or circuit breaker box. Nowadays, they are likely to be plastic. But that is ok since a ground wire is standard. When your house was built, they probably still used metal boxes. Even though the outlet was two prong, sometimes the box itself was still grounded.
If the box is not grounded a GFCI will at least protect you and your family.
Even if the box is grounded, protect the kitchen/bath outlets with a GFCI. You only need one GFCI per circuit as long as its the first outlet coming from the breakers/fuses. Wired correctly, it will protect all other circuits downstream from it.
As for safety - installing a 3-prong that is not properly grounded nor protected by a GFCI is more dangerous than the two-prong it relaces.
BTW - the B&D book is a very good reference.
The first way is that the box is supplied by an armored cable (BX or Greenfield). In this situation the metal sheathing that covers the wire acts as the ground as it connects to the back of the electrical box and to the panel.
The second way is that a bare copper wire is run from the electrical box back to the panel.
I found a strange way of grounding an electrical box in my own house which was build in the mid 50's. I replaced an electrical box that I thought was supplied by a two wire cable. When I removed the box from the wall I found a ground wire attached to a screw on he back side of the electrical box. The side of the cable had been split and the ground wire pulled back so that the ground wire never entered the box. This box had never been replaced so that work had to be origal. I had never heard of this before or since and do not think that this is a common practice.