if you are going to use it for programming and other simulation softwares, then i would suggest u get a notebook with a decent processor + RAM (at least 1GB).
When u mean designing software, do u mean graphic designing? If so do u need a dedicated graphics card for that?
You have to decide what specifications u want for your notebook, and also whether if you have any brand or notebook size preferences?
As for warranty, Dell has pretty good after sales service. Extend the warranty to 3 years if it is necessary.

Actually i think u should have tried posting in the thread "Buying new laptop? Need RECOMMENDATION???"