First thing is first, back up your ini's and remove them from the folder, open the Skyrim Launcher, click ultra, and then lower your shadows down to high quality. At this point, you might want to tone down the Anti Aliasing to 4 (personally I turn both AA and AF down to 0 and run it out of my CCC at 4x multi sample AA and 16x AF)
Open up your Skyrim.ini and at the botom of [Display] add;
fSunShadowUpdateTime=0.000
fSunUpdateThreshold=0.100
Save it and close.
Now open up your SkyrimPrefs.ini and change the following values;
fInteriorShadowDistance=2500.0000
fShadowDistance=3000.0000
iShadowMapResolutionSecondary=1024
iShadowMapResolutionPrimary=2048
bTreesReceiveShadows=1
bDrawLandShadows=1
iShadowMaskQuarter=6
iShadowMapResolution=4096
bDrawShadows=1
Save it and close it. This will hit you at about 3 - 10 FPS depending on your rig, location, and extra tweaks you add.
Try it out and let me know if it helped.

