O.K. - I try:
your error message is during boot-up - does it still boot despite this message?
the error message indicates, that there is something wrong (or missing, as you said you deleted something) with drm and your (intel ?) graphics-card.
Now - drm is part of the kernel-drivers for your card.
So I would suggest reinstalling your kernel including the modules.
You did not compile the kernel yourself - did you?
If you did and did not change the source-tree since your last install, then you could just go there and do "make install" and "make install_modules" again - then "depmod -a" to recreate the module-dependencies - and you are all set. Else install from your packages which I hope you still have.
More unlikely, but not impossible, is a missing (deleted) file in your XServer - if the above one does not fix it - try reinstalling X, too.
Next time be careful what to delete while you are root - this would not have happened would you have been working as a normal user...