Photoshop :: Image Issue - Aspect Ratio

I have run into an aspect ratio (i.e., 1.25 vs. 1.33) issue for my images (using PhotoShop and/or Microsoft PhotoEditor):

I've created documentation for nearly ten years for an older type company using a CRT monitor. The monitor allowed me to use all resolutions when working with images without any screen degradation. Generally I used a resolution of 800 by 600 but would change, if necessary, due to the project. At this point, I've been given a new LCD monitor and am at the mercy of its native resolution (i.e., 1280 by 1024) even at a higher DPI. In other words, if I work with images and text other than its native resolution (i.e., highest resolution), their appearance is distorted and/or blurred. Since my documentation is image and/or graphics intensive, this is an issue for me to consider.

The first issue regarding this change came about this week. I was asked to revise a section of a manual I created awhile ago. Thus, I found myself saving images in a screen resolution of 1280 by 1024. The original document saved images in a screen resolution of 800 by 600. I feel I can get away with things if its only a few images. However, if I have to revise complete sections; I just don't think things look consistent. For one thing, I'm now using ClearType Font on the LCD monitor vs. the old CRT.

I would like to see if there is a way to somehow change an image saved in 1280 by 1024 screen resolution to 800 by 600 (with similar quality when revising documentation). If not, I think I'll inquire about using two monitors at my desk - using the CRT for revised documentation and LCD for new projects. Agree/Disagree with this scenario?