I have found several shells i like, most changing everything compelty and allowing a lot of customization. If you didnt know, these programs change what runs instead of explorer.exe, and as your not modifiying windows, execpt for changing what is going to start up, your not breaking any rules.
These two are ones you have to buy, but they are really good.
Aston Shell
http://astonshell.com/
Quite good use of plugins, easy to setup, looks good, and has a large community base
Talisman 2
http://www.lighttek.com/talisman.htm
Quite close to what aston shell is like, requires a bit more work, but there is a large amount of use of menus and other cool effects
HoverDesk
http://www.hoverdesk.net/
Not as good as the other two. Decent fanbase, not too many features.
Free Shells
Litestep
http://www.litestep.net/
Free, but requires a large amount of setup. Hard to get working, i didnt really like it, but it seemed more for people with a lot of times on there hands
Darkstep
http://www.darkstep.com/
Basically the same as above, adds in new stuff and fixes bugs
I'll add more once i find more good ones.

