If you're having trouble opening the file you probably don't have nearly enough RAM. I haven't downloaded it myself, but if it's 30MB in Photoshop format then it's probably much, much larger than that when expanded into memory. If it's 31"x15"@300dpi...
31" * 300dpi = 9300 pixels wide
15" * 300dpi = 4500 pixels high
9300 * 4500 = 41,850,000 pixels total
assuming it's 32 bits per pixel (may be 16 or 24, but i doubt it)
41m pixels * 32bpp = 1,339,200,000 bits
So, assuming i did my math correctly (no guarantees
) you're looking at a file that's roughly 160MB uncompressed in memory. Multiple layers will make it even larger. If you don't have 256MB of RAM don't even bother trying to open it. If you have 256MB+ then give it some time because it's probably still going to hit the hard drive cache pretty hard.