If your friend simply wants to send/receive bitcoins then downloading the whole blockchain is not necessary, he could download a lightweight wallet such as Electrum. If he wants to run a full node however, then 120GB is small and won't suffice him, assuming that he is going to install Bitcoin Core for that matter, he could change the location for the folder that goes to the AppData folder by default to his 1TB HDD.
hey OmegaStarScream, thanks for the input, that was basically his question... could I operate with a full node in the 1TB HD? (considering speed and considering the O.S is not installed there). I had serious doubts about it and thought it will be better installed in the ssd HD, as Welsh said before.
I will tell him about all your suggestions, thanks a lot (he'll probably decide to use Electrum, although he wants to buy the new machine either way)