Hey guys, first time posting, long time lurker...

I've come into an old trek 4100, frame is in mint condition, I've decided to upgrade everything else.
I know its not the best frame in the world, but I get a real kick out of the building it all myself part

Anywhooo...

I have to admit I've got a bit stuck, and wondered if anyone here could lend me a hand.
Everything has worked fine until I got to sticking the chain on and the rear derailer.
I've upgraded it from a 7 speed tripple, to a 9 speed tripple (with a new crankset and shifters).
When its on the smallest sproket and chainring the derailer is almost in its out of the box position (Will post some pictures when I get chance), so almost completely folded, and the chain rubs against itself.
Then in the higher gears it seems like the derailer is too streched out.
Any help would be massive appreciated!
And you get a medal for understanding what I've just written!

Cheers all