How to change the photo resolution from low to high?

I just got my wedding photography CD's and all the pictures look grainy. This is not the case on the photographer's end, every picture is clear as a bell. I tried printing some off at Walgreens to see if maybe it was just my computer but they developed grainy as well. I was wondering if I needed to change the resolution somehow?

I uploaded some of them to Ritz's site to be developed, wanting to make a 5x7 however their site popped up a box telling me that the resolution of the picture was too low to print a good 5x7. I have the Gimp program already; I just need someone to Please tell me how I can simply fix this problem. I can't develop any of our wedding pictures to hang up. Someone please help! Thanks!

ps--The pics were taken with a Nikon D80, which I believe is 8mp.

You simply can't.

It's time to read over that contract you signed. Did your photographer sell you full resolution copies or just ones to view on your computer/TV?

You can't make low resolution photos into high resolution photos. You can try, but it won't work.

This is why the photographer gave you low resolution proofs, so you wouldn't steal the images from him/her. If you want high-res files or prints, you BUY them from the photographer.

This was done on purpose.

You may want to re-read your contract. The money you have paid already is just to cover the photographer's time of taking your wedding photos. If you want to buy their hi-res files or prints then that will cost more.

Again, just depends on the contract you agreed to.

It sounds like your photographer gave you a low resolution file to begin with. It is one thing for there to be a high res file with grain from say the photo being taken with a high iso. I really don't think there's much you can do if its a low res photo.

I would see what the file size is of the photos you have, then see what the file size is that your photographer has. Not enough pixels to print a 5x7 really sounds like these are a very low res file.

It probably states in your contract that you will get proofs or low resolution photos. In that case, many photographers will offer to give you the photos that can only be printed at 4x6 size. If that is the case, when you enlarge it it will appear grainy.

If the contract does not state that your are suppose to get low resolution, rather high resolution, then request the files again. It all goes back to your contract. You probably will have to pay more money to get the files at a higher resolution.

Also, in most states to print photos at a 3rd party location you need proof of copyright. If you have proof of copyright, then it should state at what resolution you have the rights to. If there's no stipulation, and it states that you do have copyrights, then you should be entitled to the full resolution files. That could be your legal way to get the files.