Try the LOSI installer. (why isn't it in downloads yet?)

also, you will have to be a little more specific. what theme are you using (i assume the default, austry). what happens when you click on the "start menu"(actually called popup in LS, i think). do you have a "desktop", do you have desktop icons, what features in specific work? what don't? "some of the system tasks..." is not very specific. what if you open "My Computer", and try to run a program from there (in the program files directory is a good place to look). if you can't open My computer, open taskmgr with Ctrl+Shift+Esc, and attempt to run them from there (File, Run). then, report your findings and i will do my best to help you.

Best of luck,
Crazy2be