The program is working exactly how it should. It is downloading blocks and verifying them to make sure they correctly relate to the blockchain and are not fake/with errors/whatelse. Otherwise you would risk to download random data.
It is NOT intensive. If that software create so many problems to your computer, then the computer have problems. Serious problems.
It is quite intensive, the verification uses up to 80% of my Phenom 2 X6 1100 (all six cores) and the temp goes 15° C up (from 30 to 45).