using VirtualAlloc won't help you, Say you use VirtualAlloc to allocate 4MB for your image, and the load your image into that array, you will still have to create your 4MB Bitmap, and then at some point you will have to transfer your array to a bitmap, and then again your bitmap will take up 4MB (assuming it's a 8000*480 pixel image), copying your inmemory array to the bitmap means you need to get to the BitmapData of the bitmap (Which again can add yet another 4MB to your memory needs), and then copy the array you loaded into the bitmapdata array (assuming you get the raw bits).
I personally would use the following sollution, which might sounds like some work, but if the panoramic view is the main feature of your application it's well worth it.
Depending on the need to scroll horizontal, or horizontal and vertical. (You state you even want to zoom the image, so i assume you also want to scroll horizontal and vertical) i would first make sure my image is already in 565 pixelformat, then i would divide the image into rectangles (if you only use horizontal scrolling, you can use stripes) (for example rectangles of 64*64 pixels), (Depending on the image type you could even compress the rectangles using SharpZLib for example, but that depends on the amount of compression you get, if you created the Bitmaps using a JPG image, don't bother) then i would save a special file consisting of a header with some information (imagewidth/height, blocksize, and a list of index into the file for each rectangle), then in my application i would create a single bitmap larger then the image i want to display (if the you want to display the image as 640/480 i would use an image of 640+64+64 pixels by 480+32+64+64 pixels, the +32 bits is to get the image to multiple of my used blocksize)
Then i would ovverride the paint function of a panel to Paint my image into the Graphics object of that panel, The complex part of this is if you want to be really effecient, you should not need to load all the rectangles again if you move your view 1 rectangle to the left for example, you can for determine with chuncks of the image i want to display, and load them in part by part) when scrolling you can cleverly determine which additional rectangles you need to load in, you can actually load them in ahead of time to create a smooth scrolling).
example, assume you have an image that looks like this, every letter is a 64*64 block, and assume our screen is 5 characters wide, we start out viewing the left 5 characters, our inmemory image is 7 blocks big
abcdefghijklmnopqrstuvwxyz
i would load 6 blocks into my inmemory buffer, and draw the image to the screen from the first block (a) to the 5th(e)
abcdefx
now after i scroll 64 pixels to the right, my in memory image looks like below, and i draw the image from the second block (b) to the 6th(f)
abcdefg
Now scroll another 64 pixels draw the image from (c) to (g)
hbcdefg
Scroll yet another 64 pixels now it becomes interesting i have to draw in 2 passes first the left part (d)-(g) then the last block(h)
hicdefg
etc, etc,etc, this way while youre scrolling you only need to loadahead 1 stripe of rectangles to keep it smooth.
Well, this might not be the most easiest sollution to make, but it would atleast be very memory conservative, i hope you understand what i mean because i might not have explained it to well, 