should I feel guilty right now?

I feel really guilty right now. I feel as if, like usual, I should help my dad with his computer. However, also, as usual, he won't take my advise and is just using me for my computer savvy. Ever since I had started helping my dad with his computer problems, he has ignored my advice. He frequently downloads and uses random software not knowing what it does or where it came from. He'll constantly change his security software, install applications that do things Windows already is capable of naturally, and even make random online friends that he's never met. He treats his computer like a toy, not a tool, and I've been telling him to smarten up for years, and take my advise. I have learned well what he understands with computers, and would never say anything that he wouldn't understand.

I have gotten so tired of him ignoring my advise that tonight I told him I would not help him with his Internet Explorer. It seemed like if I had fixed his IE issue, that would allowed him to be reckless and download more software that could potentially cause damage. At dinner, I was very diplomatic when I told him that I wouldn't help him tonight. I told him how it is, and that's it. Regardless, he started to argue with me and I felt belittled.

I feel guilty for not helping him, but I've lost his trust. He has broken so many promises.

Should I feel guilty for not helping and just do it, or am I just in not helping him this time?

thanks guys in advance

same things happening with me but it happens when IM doing something like making a model my dad thinks i cant do crap
but you know if hes treating his computer like a toy you know its his fault
help him fix it and let him kill his pc once that happens tell him you wont help him
THEN tell him why his pc crashed and tell him he better take your advise or you wont fix the pc
now maybe others will have a differnt ideas
my idea might work but if you feel its not a good one thats allright

if he bought it let him do what he wants with it, if he runs it into the ground its not your problem

I've tried to tell him why he the one causing the computer to break.

I believe he knows that, but he hasn't come to terms with it. He has acknowledged that I am handy with computers, but he really tries not to believe he's being reckless. He will frequently lie about the amount programs he's installed on the computer per day, claiming that he hasn't installed anything lately. By looking the start menu, I learned that he's installing two apps a day on average. This is not good.

I think he treats his computer as a toy because he's bored. He knows better than to do that, because he lies about the amount of programs he's installed, and I've directly shown him what he's doing to his computer. He has a bad habit he does care to break.

thank you for the suggestion psychomantis. If only my dad actually accepted he is causing problem...