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.
Well, I don't know about calling it "NOT intensive." The wallet program has to download all the blocks, hash each of them to ensure they meet the criteria and are indeed a part of the block chain, then scan each block for a transaction with a wallet address that the client owns. At least, that's my understanding of it. My laptop gets pretty warm when it goes on a long catch up run, but not 100C hot!