My uncle have been experiencing window virus..etc. Since he not very computer savvy, I thought of getting him an mac mini. I am not too familiar with Mac hardware. If I get him a mini Mac, can I use it with a Dell monitor?
Yes, it will work. The Mac Mini comes with a DVI monitor cable, so if your Dell monitor has a DVI input, which, if it was made in the past 5 years or so it almost certainly does, it'll work just fine.