The Image will be the same, so long as it's Opened in PS with the same calibration.
When one views in other programs, and especially in non-Color Managed environments, there is no control over how the Image will display. The same can happen in Color Managed software, if they are calibrated differently.
Which programs are you using to view the Image? How are the computers, with those programs calibrated?
I created my photo in photoshop exactly as I wanted it. But when I saved it to my computer (and viewed it on two other computers as an attachment) it was much darker. Why is that? I want the version in photoshop to be the same one as the one saved on the computer screen.
Then edit and save your imags all in the sRGB color space. None color manage programs display all images regardless of what color space is their profils as though they all had sRGB profiles. They simply use a pixel three rgb value as though they are sRGB color space values. If pixels have values for a different color space the colors use to display the image will be off.
You don’t necessarily need to set sRGB as your working colorspace in PS, but you should save the final images in sRGB if you want to view them on another computer that may or may not be color-managed. Browsers are supposed to display things in the sRGB colorspace if they don’t have any way of doing something better—for example if the image doesn’t’ have a color-profile specified or if the browser doesn’t know how to color-manage things.
Why is that?
Welcome to the realm of color-management, where calibration and profiling and an understanding of the use of color spaces is required to be able to get repeatable results.
Know these things:
1. It has been proven time and again that a person cannot gain a working knowledge of color-management by asking questions on a forum. It's too complex for that, and inevitably tempers flare. And make no mistake - you have to learn it, because there really are no ''set it this way and forget it'' answers!
2. Not all applications are color-managed, so even on a super-high-end system set up by a professional who knows what he's doing, there are times when color mismatches are expected (for example between what you see on a high end monitor in Photoshop vs. what you see in Internet Explorer). Understanding color-management is required for you to be able to understand when this is and ignore it or deal with it.
Best of luck to you. Understanding color-management will be a step toward making better images.
Or it could be as simple as the other PC monitors are set to darker brightness and/or more or less contrast etc.
Try any image, for example a pic from Google images or a photo from your camera directly as .jpg and not processed in any way on your PC (not even seen by Ps) and see if you get the same results.
Try setting each monitor/PC to some basic setup (not color managed) as a starting point...such as with:
(this is NOT a substitute for managed color)