Please don't follow Funnybunny's suggestion unless you're desperate. Unless frame rate is more important to you than anything else, it's probably not necessary to use it. I ran Skyrim on a very low-end computer for years and was able to get decent performance while using lots of graphics mods (and others)
They are several things you can try. "Bethesda High Performance Textures" by Gamwich (there are two files, so look for both) is a must have, even if your system is higher-end. It replaces hundreds of textures with smaller files that in most cases actually look better.
http://www.nexusmods.com/skyrim/mods/42360/?
http://www.nexusmods.com/skyrim/mods/43921/?
Another must have is "Skyrim Project Optimization", which uses occlusion culling to reduce the number of things that Skyrim has to render in interiors (things you can't see anyway). http://www.nexusmods.com/skyrim/mods/32505/?
You can try "HiAlgo Boost", which dynamically reduces texture resolution when you're moving. If his game becomes a slideshow when he's in combat, for example, this can help make it playable. http://www.nexusmods.com/skyrim/mods/15123/?
There are other programs and other techniques. Look for them. Experiment with settings (carefully....if something promises the moon, it's probably nonsense, dangerous or both) He should resist playing with ridiculously crap textures or without shadows or any of those "fixes" unless absolutely necessary.