although a better graphics card is advised, try tweaking some of the settings in skyrimprefs.ini and the other file.
also try changing some things via the console.
you can get almost decent FPS if:
1. you run it on the lowest resolution: 600X800
2. in the launcher: go to settings, advanced, and set everything to low, disable reflections, set everything to minimum.
3. backup skyrimprefs.ini and change the settings on things that seem like you dont need them (shadows, decals...)
~such as: Turn off/lower the shadows
~~open SkyrimPrefs.ini with notepad and change iShadowMapResolution=(#) to 0. You'll be better off just turning shadows down to low, however; removing them completely only hurts your FPS.
4. during gameplay press the tilde key (~or`) and enter these things:
~~~~~~most of these are toggles: put in first time: ON, put in again: OFF~~~~~
~A. type in without the parenthesis [TEOFIS] - disables the radial blur effect, makes the game less pretty but will boost FPS by a bit (around 5-10 frames)
~B. type in without the parenthesis [TG] toggles the grass display- grass will look weird, but will boost your FPS outside.
~C. [TT] culles the treees - makes them almost clone-simmilar, and less "lighter" to draw for the computer
~D. [TS] if you are desperate - "disables" the sky. the sky will be just black with no clouds, stars, sun, etc. you will still be able to see everything, but it will look a little strange (will boost fps by a lot on some computers)
~E. change the FOV (field of view) by typing in [FOV ##] where ## is a number between 65-180. it is default at 65, but you can change this... (this is not a toggle, if you change it, you have to change it back by typing in [fov 65]
~~~~~~~~~~~~~~~~~~~~~This page has more resources(tweaks,mods for performance)~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
http://forums.steampowered.com/forums/showpost.php?p=26407737&postcount=88
~~~~~~~~~~~~~~~~~~~~~Use the Vista Services Optimizer "Game Mode" to stop the non-essential programs/services and than to restart them when you are done playing games...~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
http://download.cnet.com/Vista-Services-Optimizer/3000-2094_4-10890033.html