Save both sides of your layout, and save them to a directory. Don't worry if there's a significant overlap between the two scanned areas - that's GOOD, and will make the finished product easier to create.
Open the two halves in Paint Shop Pro. Look at the side that was "bent" in the scanner for each half - if there is a dark area at the edge of that side, crop off the darkened area. Use the selection tool, and draw a box to select everything BUT the darkened area. Then, crop to the selected area - Image, Crop to Selection from the menu, or on the keyboard.
Go to Image, Resize, or from the keyboard, and resize each half of the image. Set the Height to 800 pixels, and make sure that Resize type is set to Smart Size from the drop down menu. (For version 8 or 9, choose Pixels as the measurement unit from the drop down box at the right side of Pixel Dimensions) Set the resolution to 72 dpi.
Now, create a new image - File, New from the menu. I like to create an image 1200x1200 pixels, so I have a large canvas to adjust my two halves.
Go to the first half of your layout, and choose Edit, Copy from the menu. Select your new image, and choose Edit, Paste, As New Layer from the menu.
Maneuver this half of the layout to the appropriate side of the new image. v7 will let you move the layer automatically - for v8 or v9, choose the Move tool from the left side of the screen, and then move the layer. Repeat the process with the second half of the layout - copy it out to the clipboard, and paste it in as a new layer.
Move the second layer over top of the first, and line up the "cut" edges until they match. If you need a closer look, go to View, Zoom in by 1 from the menu until you have a comfortable view point.
When the two halves are lined up, and you're happy with the positioning, go to Layers, Merge, Merge All (Flatten) from the menu. Use the select tool to draw a box around your layout, and Image, Crop to Selection to eliminate the white outside space.
Save your new image - if you've used the 800 pixel value that we began with, your layout is correctly sized to upload to scrapbook.com!