How do you define "hi-res"? Digital cameras don't take images with a specific dpi; they take pictures with a certain number of pixels. So the size you need to print will determine what "hi-res" means.

300 dpi is what our Media Services need.

How can I figure that out based on pixels?

I tried resizing and the no. of dpi's stays the same.

300 dpi means 300 pixels per inch. Multiply 300 times the size in inches to determine the minimum number of pixels. So, for example, if you need the image to be printed at 3" by 5", then it needs to be at least 900 pixels by 1500 pixels.

What are you using for your graphics software?

irfanview

It seems to be letting me resize by changing the dpi, does that seem likely?

I've never used irfanview. That said, ...

It seems to be letting me resize by changing the dpi, does that seem likely?

There's two different types of "resizing". You can resize by reducing the number of pixels. This involves resampling the image and results in a loss of quality (fewer pixels means lower quality). You can also resize by increasing the dpi, but keeping the total number of pixels the same. This makes the image print smaller, but keeps the intrinsic image the same.

Does it tell you the dimensions in pixels before and after you resize? If those numbers don't change, then irfanview is letting you do the latter form of resizing. This is good and is probably what you want.

Okay - I also checked the size of the file and it does seem to increase when I do that.

(I also emailed one of them to the photo manager to see if it fit into their specs.)

What format is the file before and after you do your thing? If it's a jpeg, you might be better off sending the original image to the photo manager, since jpegs lose quality every time you resave them.

He won't use it if it's less than 300 dpi.